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Following is my code, which is working fine in most scenarios except in case of leading Zeros. It should preserve trailing zeros like -001 + 1 = 002
Code -
function incrementString (str) {
if(str === '') return "1";
if(!str.slice(-1).match(/\d/)) return `${str}1`;
const replacer = x => {
// Check if number
return (parseInt(x) + 1).toString();
}
return str.replace(/\d+/g, replacer )
}
// Return foobar2 which is correct
console.log(incrementString("foobar1"))
// Return foobar100 which is correct
console.log(incrementString("foobar099"))
// Return foobar2 which is incorrect, is should be foobar002
console.log(incrementString("foobar001"))
// Return foobar1 which is incorrect, is should be foobar001
console.log(incrementString("foobar000"))
// Return foobar101 which is incorrect, is should be foobar0101
console.log(incrementString("foobar0100"))
You may use this regex soluton:
function incrementString (str) {
if(str === '') return "1";
if(!str.slice(-1).match(/\d/)) return `${str}1`;
const replacer = (m, g1, g2) => {
// Check if number
var nn = (g1?g1:"") + (parseInt(g2) + 1).toString()
return nn.slice(-1 * m.length)
}
return str.replace(/(0*)(\d+)/g, replacer )
}
// Return foobar2
console.log(incrementString("foobar1"))
// Return foobar100
console.log(incrementString("foobar099"))
// Return foobar002
console.log(incrementString("foobar001"))
// Return foobar001
console.log(incrementString("foobar000"))
// Return foobar0101
console.log(incrementString("foobar0100"))
// Return foobar01000
console.log(incrementString("foobar00999"))
// Return foobar010
console.log(incrementString("foobar009"))
Everything seems to be perfect, you need to only handle the regex part of the leading zeroes in your replacer function.Below is the updated code for the same.
function incrementString(str) {
if (str === '')
return "1";
if (!str.slice(-1).match(/\d/)) {
return `${str}1`;
}
const replacer = x => {
var leadingZerosMatched = x.match(/^0+/);
var incrementedNumber = (parseInt(x) + 1).toString();
var leadingZeroes;
if (leadingZerosMatched && incrementedNumber.length < x.length) {
leadingZeroes = leadingZerosMatched[0];
if(leadingZeroes.length === x.length) {
leadingZeroes = leadingZeroes.slice(0, leadingZeroes.length-1)
}
}
return leadingZeroes ? leadingZeroes + incrementedNumber : incrementedNumber;
}
return str.replace(/\d+/g, replacer)
}
You could split your string from digits and use padStart after increment to preserve leading 0:
const incrementString = (str) => {
const [chars, nums] = str.split(/(\d+)/)
return [
...chars,
String(Number(nums) + 1)
.padStart(nums.length, '0')
].join('')
}
console.log(incrementString("foobar1"))
console.log(incrementString("foobar099"))
console.log(incrementString("foobar001"))
console.log(incrementString("foobar000"))
console.log(incrementString("foobar0100"))
function incrementString (str) {
let [
openingPartial,
terminatingInt
] = str.split(/(\d*)$/);
if (terminatingInt) {
const incrementedInt = String(parseInt(terminatingInt, 10) + 1);
const leadingZeroCount = (terminatingInt.length - incrementedInt.length);
if (leadingZeroCount >= 1) {
terminatingInt = Array(leadingZeroCount).fill("0").concat(incrementedInt).join('');
} else {
terminatingInt = incrementedInt;
}
} else {
terminatingInt = '1';
}
return `${ (openingPartial || '') }${ terminatingInt }`;
}
// Should return 'foo_003_bar1'.
console.log(incrementString("foo_003_bar"));
// Should return 'foo_003_bar_01'.
console.log(incrementString("foo_003_bar_00"));
// Should return 'foobar1'.
console.log(incrementString("foobar"));
// Should return 'foobar2'.
console.log(incrementString("foobar1"));
// Should return 'foobar100'.
console.log(incrementString("foobar099"));
// Should return 'foobar002'.
console.log(incrementString("foobar001"));
// Should return 'foobar001'.
console.log(incrementString("foobar000"));
// Should return 'foobar0101'.
console.log(incrementString("foobar0100"));
.as-console-wrapper { max-height: 100%!important; top: 0; }
I am trying to expand an algebraic term.
(x+1)(x+1)/x => x + 2 + x^-1
(x+1)^3 => x^3 + 3x^2 + 3x + 1
(x^2*x)(x^2) => x^5
This is my attempt at it. I have tried a lot of ways trying to fix the problems below.
Problems:
Like terms should be added together
(x+1)(x+1)(x+1) should be valid.
(x+1)^2 should be equal to (x+1)(x+1)
x(x+1) should be valid
1x^n should just be x^n
There should be no 0x^n terms.
nx^0 terms should just be n
Code Snippet:
function split(input) {
return ((((input.split(")(")).toString()).replace(/\)/g, "")).replace(/\(/g, "")).split(','); }
function strVali(str) {
str = str.replace(/\s+/g, "");
var parts = str.match(/[+\-]?[^+\-]+/g);
// accumulate the results
return parts.reduce(function(res, part) {
var coef = parseFloat(part) || +(part[0] + "1") || 1;
var x = part.indexOf('x');
var power = x === -1 ?
0:
part[x + 1] === "^" ?
+part.slice(x + 2) :
1;
res[power] = (res[power] || 0) + coef;
return res;
}, {});
}
function getCoeff(coeff) {
var powers = Object.keys(strVali(coeff));
var max = Math.max.apply(null, powers);
var result = [];
for(var i = max; i >= 0; i--)
result.push(strVali(coeff)[i] || 0);
return result; }
function evaluate(expression) {
var term1 = getCoeff(expression[0]);
var term2 = getCoeff(expression[1]);
var expand = "";
for ( var j = 0; j < term1.length; j++ ) {
for ( var i = 0; i < term2.length; i++ ) {
expand += Number(term1[j] * term2[i]) + 'x^ ' + (Number(term1.length) - 1 - j + Number(term2.length) - 1 - i) + ' + ';
}}
var final = "";
for ( var Z = 0; Z < getCoeff(expand).length; Z++) {
final += ' ' + getCoeff(expand)[Z] + 'x^ {' + (getCoeff(expand).length - Z - 1) + '} +';
}
final = "$$" + ((((((final.replace(/\+[^\d]0x\^ \{[\d]+\}/g,'')).replace(/x\^ \{0}/g,'')).replace(/x\^ \{1}/g,'x')).replace(/[^\d]1x\^ /g,'+ x^')).replace(/\+ -/g,' - ')).slice(0, -1)).substring(1,(final.length)) + "$$";
document.getElementById('result').innerHTML = final;
MathJax.Hub.Queue(["Typeset", MathJax.Hub, document.getElementById('result')]);
}
function caller() {
var input = document.getElementById('input').value;
evaluate(split(input)); }
div.wrapper {
width: 100%;
height:100%;
border:0px solid black;
}
input[type="text"] {
display: block;
margin : 0 auto;
padding: 10px;
font-size:20px;
}
button{
margin:auto;
display:block;
background-color: white;
color: black;
border: 2px solid #555555;
padding-left: 20px;
padding-right: 20px;
font-size: 20px;
margin-top:10px;
}
button:hover {
box-shadow: 0 12px 16px 0 rgba(0,0,0,0.24),0 17px 50px 0 rgba(0,0,0,0.19);
}
<script type="text/javascript" async
src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-MML-AM_CHTML">
</script>
<div class='wrapper'><input id="input" title="Enter Expression" type="text" value="(x^2+x+1)(x^2+x+1)"></div>
<div> <button onclick="caller()">Click</button></div>
<div id="result">$$x^4 + 2x^3 + 3x^2 + 2x + 1$$</div>
Reference:
How to calculate coefficients of polynomial expansion in javascript
Getting coefficients of algebraic term
How to get a term before a character?
Edit: I have re-written my original answer from when the question did not include the - and / operators). My new answer supports - and /.
Since you have not defined a precise grammar, I have made some assumptions. I support the +, -, /, ^ operators and the implicit multiply. These can operate on numbers, x and (...) expressions, except that right hand side of the ^ operator must be a number. I allow spaces between tokens.
Limitations: The -is a binary not unary - operator, So x-2 if OK, -2 on its own is a syntax error. The / is limited. You may divide by a value with a single coefficient such as 2, 'x', 2x^2, but not by cannot have 1/(x^2+1), which would evaluate to an infinite series.
It first takes the string and wraps it in a 'tokenizer' which lets you look it one token at a time, where a token is a number, x, ( ) or operator.
It then calls evaluateSum() which evaluates things separated by + or -, where each thing is a product evaluated by evaluateProduct(). This in turn uses evaluatePower() to evalue the ^. Finally evaluateTerm() looks for x, numbers and bracketed sub-expressions which are evaluates recursively with evaluateSum(). This hierarchy creates the correct operator precedence and evaluation order.
Each layer of the evaluation returns a 'coefficients' object which s array-like, but may contain megative indexes. For example [1,0,1] means 1+x^2.
It can cope with any number of nested brackets and a lot of other case such as xx(x) is x^3, 2^3 is 8. I have added a few throws for syntax errors, for example 2^x is illegal.
function makeTokenizer(source) {
var c, i, tokenizer;
i = 0; // The index of the current character.
c = source.charAt(i); // The current character.
function consumeChar() { // Move to next c, return previous c.
var prevC = c;
i += 1;
c = source.charAt(i);
return prevC;
}
tokenizer = {
next : function () {
var str;
while (c === ' ') { // Skip spaces
consumeChar();
}
if (!c) {
tokenizer.token = undefined; // End of source
} else if (c >= '0' && c <= '9') { // number
str = consumeChar(); // First digit
while (c >= '0' && c <= '9') { // Look for more digits.
str += consumeChar();
}
tokenizer.token = Number(str);
} else if (c === "x") {
tokenizer.token = consumeChar();
} else { // single-character operator
tokenizer.token = consumeChar();
}
}
};
tokenizer.next(); // Load first token.
return tokenizer;
}
function makeCoefficients() { // Make like an array but can have -ve indexes
var min = 0, max = 0, c = {};
return {
get: function (i) {
return c[i] || 0;
},
set: function (i, value) {
c[i] = value;
min = Math.min(i, min);
max = Math.max(i + 1, max);
return this; // for chaining
},
forEach: function (callback) {
var i;
for (i = min; i < max; i += 1) {
if (this.get(i)) {
callback(this.get(i), i);
}
}
},
toString: function () {
var result = "", first = true;
this.forEach(function (val, power) {
result += (val < 0 || first) ? "" : "+";
first = false;
result += (val === 1 && power !== 0) ? "" : val;
if (power) {
result += "x";
if (power !== 1) {
result += "^" + power;
}
}
});
return result;
},
toPowerOf: function (power) {
if (power === 0) {
return makeCoefficients().set(0, 1); // Anything ^0 = 1
}
if (power === 1) {
return this;
}
if (power < 0) {
throw "cannot raise to negative powers";
}
return this.multiply(this.toPowerOf(power - 1));
},
multiply: function (coefficients) {
var result = makeCoefficients();
this.forEach(function (a, i) {
coefficients.forEach(function (b, j) {
result.set(i + j, result.get(i + j) + a * b);
});
});
return result;
},
divide: function (coefficients) {
// Division is hard, for example we cannot do infinite series like:
// 1/(1 + x^2) = sum_(n=0 to infinity) 1/2 x^n ((-i)^n + i^n)
// So we do a few easy cases only.
var that = this, result = makeCoefficients(), done;
coefficients.forEach(function (value, pow) {
that.forEach(function (value2, pow2) {
result.set(pow2 - pow, value2 / value);
});
if (done) {
throw "cannot divide by " + coefficients.toString();
}
done = true;
});
return result;
},
add: function (coefficients, op) {
var result = makeCoefficients();
this.forEach(function (value, i) {
result.set(value, i);
});
op = (op === "-" ? -1 : 1);
coefficients.forEach(function (value, i) {
result.set(i, result.get(i) + value * op);
});
return result;
}
};
}
var evaluateSum; // Called recursively
function evaluateTerm(tokenizer) {
var result;
if (tokenizer.token === "(") {
tokenizer.next();
result = evaluateSum(tokenizer);
if (tokenizer.token !== ")") {
throw ") missing";
}
tokenizer.next();
} else if (typeof tokenizer.token === "number") {
result = makeCoefficients().set(0, tokenizer.token);
tokenizer.next();
} else if (tokenizer.token === "x") {
tokenizer.next();
result = makeCoefficients().set(1, 1); // x^1
} else {
return false; // Not a 'term'
}
return result;
}
function evaluatePower(tokenizer) {
var result;
result = evaluateTerm(tokenizer);
if (tokenizer.token === "^") {
tokenizer.next();
if (typeof tokenizer.token !== "number") {
throw "number expected after ^";
}
result = result.toPowerOf(tokenizer.token);
tokenizer.next();
}
return result;
}
function evaluateProduct(tokenizer) {
var result, term, divOp;
result = evaluatePower(tokenizer);
if (!result) {
throw "Term not found";
}
while (true) {
divOp = (tokenizer.token === "/");
if (divOp) {
tokenizer.next();
term = evaluatePower(tokenizer);
result = result.divide(term);
} else {
term = evaluatePower(tokenizer);
if (!term) {
break;
}
result = result.multiply(term);
}
}
return result;
}
function evaluateSum(tokenizer) {
var result, op;
result = evaluateProduct(tokenizer);
while (tokenizer.token === "+" || tokenizer.token === "-") {
op = tokenizer.token;
tokenizer.next();
result = result.add(evaluateProduct(tokenizer), op);
}
return result;
}
function evaluate(source) {
var tokenizer = makeTokenizer(source),
coefficients = evaluateSum(tokenizer);
if (tokenizer.token) {
throw "Unexpected token " + tokenizer.token;
}
console.log(source + " => " + coefficients.toString());
}
// Examples:
evaluate("(x+1)(x+1)"); // => 1+2x+x^2
evaluate("(x+1)^2"); // => 1+2x+x^2
evaluate("(x+1)(x+1)(x+1)"); // => 1+3x+3x^2+x^3
evaluate("(x+1)^3"); // => 1+3x+3x^2+x^3
evaluate("(x)(x+1)"); // => x+x^2
evaluate("(x+1)(x)"); // => x+x^2
evaluate("3x^0"); // => 3
evaluate("2^3"); // => 8
evaluate("(x+2x(x+2(x+1)x))"); // => x+6x^2+4x^3
evaluate("(x+1)(x-1)"); // => -1+x^2
evaluate("(x+1)(x+1)/x"); // x^-1+2+x
//evaluate("(x+1)/(x^2 + 1)"); //throws cannot divide by 1+2x
It can handle +, -, / and implicit multiplication. It expands the parenthesis accordingly and adds them to the original expression while removing the parenthesised version. It collects like terms accordingly. Limitations: It cannot divide by a polynomial and it does not support the * operator.
function strVali(str) {
str = str.replace(/\s+/g, "");
var parts = str.match(/[+\-]?[^+\-]+/g);
return parts.reduce(function(res, part) {
var coef = parseFloat(part) || +(part[0] + "1") || 1;
var x = part.indexOf('x');
var power = x === -1 ?
0:
part[x + 1] === "^" ?
+part.slice(x + 2) :
1;
res[power] = (res[power] || 0) + coef;
return res;
}, {});
}
function getCoeff(coeff) {
var powers = Object.keys(strVali(coeff));
var max = Math.max.apply(null, powers);
var result = [];
for(var i = max; i >= 0; i--)
result.push(strVali(coeff)[i] || 0);
return result; }
function format(str) {
str = ' ' + str;
str = str.replace(/-/g,'+-').replace(/x(?!\^)/g,'x^1').replace(/([+\/*)(])(\d+)([+\/*)(])/g,'$1$2x^0$3').replace(/([^\d])(x\^-?\d+)/g,'$11$2').replace(/(-?\d+x\^\d+)(?=\()/g,'($1)').replace(/(\))(-?\d+x\^\d+)/g,'$1($2)').replace(/([^\)\/])(\()([^\*\/\(\)]+?)(\))(?![(^\/])/g,'$1$3');
str = str.replace(/(\([^\(\)]+?\))\/(\d+x\^-?\d+)/g,'$1/($2)').replace(/(\d+x\^-?\d+)\/(\d+x\^-?\d+)/g,'($1)/($2)').replace(/(\d+x\^-?\d+)\/(\(\d+x\^-?\d+\))/g,'($1)/$2');
return str;
}
function expBrackets(str) {
var repeats = str.match(/\([^\(\)]+?\)\^\d+/g);
if ( repeats === null ) { return str; } else { var totalRepeat = '';
for ( var t = 0; t < repeats.length; t++ ) { var repeat = repeats[t].match(/\d+$/); for ( var u = 0; u < Number(repeat); u++ ) { totalRepeat += repeats[t].replace(/\^\d+$/,''); }
str = str.replace(/\([^\(\)]+?\)\^\d+/, totalRepeat); totalRepeat = ''; }
return str; }
}
function multiply(str) {
var pairs = str.match(/\([^\(\)]+?\)\([^\(\)]+?\)/g);
if ( pairs !== null ) { while ( pairs !== null ) { var output = '';
for (var i = 0; i < pairs.length; i++) { var pair = pairs[i].slice(1).slice(0, -1).split(')('); var firstCoeff = getCoeff(pair[0]); var secondCoeff = getCoeff(pair[1]);
for (var j = 0; j < firstCoeff.length; j++) {
for (var k = 0; k < secondCoeff.length; k++) { output += firstCoeff[j] * secondCoeff[k] + 'x^' + Number(firstCoeff.length - 1 - j + secondCoeff.length - 1 - k) + '+'; } }
var regexp = new RegExp(pairs[i].replace(/\(/g,'\\(').replace(/\+/g,'\\+').replace(/\)/g,'\\)').replace(/\^/g,'\\^').replace(/\-/g,'\\-'));
str = str.replace(regexp, '(' + (output.slice(0, -1).replace(/[^\d]0x\^\d+/g,'')) + ')');
output = ''; }
pairs = str.match(/\([^\(\)]+?\)\([^\(\)]+?\)/g); } }
else { }
str = str.replace(/\+/g,' + ');
return str;
}
function divide(str) {
if ( str.match(/\/(\(-?\d+x\^-?\d+.+?\))/g) === null && str.match(/\//g) !== null ) {
while ( pairs !== null ) {
var pairs = str.match(/\([^\(\)]+?\)\/\([^\(\)]+?\)/g);
var output = '';
for (var i = 0; i < pairs.length; i++) {
var pair = pairs[i].slice(1).slice(0, -1).split(')/(');
var firstCoeff = getCoeff(pair[0]);
var secondCoeff = getCoeff(pair[1]);
for (var j = 0; j < firstCoeff.length; j++) {
for (var k = 0; k < secondCoeff.length; k++) {
output += firstCoeff[j] / secondCoeff[k] + 'x^' + Number(firstCoeff.length - 1 - j - secondCoeff.length + 1 + k) + '+';
output = output.replace(/([+-])Infinityx\^\-?\d+/g,'').replace(/([+-])NaNx\^\-?\d+/g,'');
} }
var regexp = new RegExp(pairs[i].replace(/\(/g,'\\(').replace(/\+/g,'\\+').replace(/\)/g,'\\)').replace(/\^/g,'\\^').replace(/\-/g,'\\-'));
str = str.replace(regexp, '(' + (output.slice(0, -1).replace(/[^\d]0x\^-?\d+/g,'')) + ')');
output = ''; }
pairs = str.match(/\([^\(\)]+?\)\/\([^\(\)]+?\)/g); } }
else { }
return str;
}
function evaluate(str) {
var result = format(divide(format(multiply(expBrackets(format((str)))))));
var resultCollect = '';
result = result.replace(/\s+/g, "").replace(/[^\d]0x\^-?\d+/g,'').replace(/\+/g,' + ');
if ( result === '') {
document.getElementById('result').innerHTML = '$$' + str + '$$' + '$$ = 0 $$';
MathJax.Hub.Queue(["Typeset", MathJax.Hub, document.getElementById('result')]);
} else if ( result.match(/-?\d+x\^-\d+/g) === null && str.match(/\/(\(-?\d+x\^-?\d+.+?\))/g) === null) {
for ( var i = 0; i < getCoeff(result).length; i++ ) {
resultCollect += getCoeff(result)[i] + 'x^' + Number(getCoeff(result).length - 1 - i) + '+' ; }
if ( resultCollect !== '')
resultCollect = '$$ = ' + resultCollect.slice(0,-1).replace(/[^\d]0x\^-?\d+/g,'').replace(/\+/g,' + ').replace(/x\^0/g,'').replace(/x\^1(?!\d+)/g,'x').replace(/\^(-?\d+)/g,'\^\{$1\}').replace(/\+ -/g,' - ') + '$$';
else
resultCollect = 'Error: Trying to divide by a polynomial ';
document.getElementById('result').innerHTML = '$$' + str.replace(/\^(-?\d+)/g,'\^\{$1\}') + '$$' + resultCollect;
MathJax.Hub.Queue(["Typeset", MathJax.Hub, document.getElementById('result')]);
} else {
resultCollect = '$$ = ' + result.replace(/\^(-?\d+)/g,'\^\{$1\}') + '$$';
document.getElementById('result').innerHTML = '$$' + str.replace(/\^(-?\d+)/g,'\^\{$1\}').replace(/\+ -/g,' - ') + '$$' + resultCollect;
MathJax.Hub.Queue(["Typeset", MathJax.Hub, document.getElementById('result')]);
}
}
function caller() {
var input = document.getElementById('input').value;
evaluate(input);
}
div.wrapper {
width: 100%;
height:100%;
border:0 solid black;
}
input[type="text"] {
display: block;
margin : 0 auto;
padding: 10px;
font-size:20px;
}
button{
margin:auto;
display:block;
background-color: white;
color: black;
border: 2px solid #555555;
padding-left: 20px;
padding-right: 20px;
font-size: 20px;
margin-top:10px;
}
button:hover {
box-shadow: 0 12px 16px 0 rgba(0,0,0,0.24),0 17px 50px 0 rgba(0,0,0,0.19);
}
<script type="text/javascript" async
src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js?config=TeX-MML-AM_CHTML">
</script>
<input id="input" type="text" title="Enter Expression: ">
<button onclick="caller()">Click</button>
<div id="result"></div>
<div id="errors"></div>
My approach utilizes two helper classes:
-Term: This stores a coefficient and an object, the keys of which are variables and the values of which are the exponents. It has methods for determining whether terms are the "same" (i.e. whether they have the same variables with the same exponents, thus allowing them to be added), adding terms, and multiplying terms.
-Polynomial: This stores an array of terms. It has methods for adding two polynomials, multiplying two polynomials, and simplifying polynomials (eliminating terms with 0 coefficients and combining like terms).
It has two substantial helper functions:
-findOuterParens - Given a string, this function returns the indices of the first outermost pair of left and right parentheses.
-parseExpressionStr - This function uses a regular expression to split a string into three types of substrings: 1) a number, 2) a symbol (i.e. a variable, like 'x' or 'y'), or 3) an operator (*, -, +, ^, /). It creates Polynomial objects for the first two types and leaves the operators as strings.
The expand function runs the show. It takes in a string and returns a Polynomial object representing the expanded form of the polynomial in the string. It does this as follows:
1) It deals with parentheses by recursion. It uses findOuterParens to find all outermost parenthsized substrings. So for "3x*(x+4)+(2(y+1))*t", for instance, it would find "x+4" and "2(y+1)" as parenthsized substrings. It then passes these to itself for further parsing. For "2(y+1)", it would identify "y+1" as a parenthesized substring, and pass this to itself, for three levels of recursion for this example.
2) It deals with other parts of the string using parseExpressionStr. After steps 1 and 2, it has an array containing Polynomial objects and operators (stored as strings). It then proceeds to simplifying and expanding.
3) It converts subtraction subproblems to addition subproblems by replacing all -'s with +'s and multiplying all polynomials following -'s by -1.
4) It converts division subproblems to multiplication subproblems by replacing /'s with *'s and inverting the Polynomial following the /. If the polynomial following the / has more than one term, it throws an error.
5) It converts power subproblems to multiplication subproblems by replacing ^'s with a series of multiplications.
6) It adds in implicit *'s. I.e. if two Polynomial elements are right next to each other in the array, then it's inferred that they are being multiplied, so, e.g. '2*x' == '2x'.
7) Now the array has polynomial objects alternating with either '+' or '*'. It first performs all polynomial multiplications and then performs all additions.
8) It performs a final simplification step and returns the resulting expanded polynomial.
<html>
<head></head>
<body></body>
<script>
function findOuterParens(str) {
var leftIndex = str.indexOf('('), leftNum = 1, rightNum = 0;
if (leftIndex === -1)
return
for (var i=leftIndex+1; i<str.length; i++) {
if (str[i] === '(')
leftNum++;
else if (str[i] === ')')
rightNum++, rightIndex=i;
if (leftNum === rightNum)
return {start: leftIndex, end: rightIndex}
}
throw Error('Parenthesis at position ' + leftIndex + ' of "' + str + '" is unpaired.');
}
function parseExpressionStr(inputString) {
var result = [], str = inputString;
while (str) {
var nextPart = str.match(/([\d]+)|([\+\-\^\*\/])|([a-zA-z])/);
if (!nextPart)
return result;
if (nextPart.length === 0)
throw Error('Unable to parse expression string "' + inputString + '". Remainder "' + str + '" could not be parsed.');
else if (nextPart[1]) // First group (digits) matched
result.push(new Polynomial(parseFloat(nextPart[0])));
else if (nextPart[3]) // Third group (symbol) matched
result.push(new Polynomial(nextPart[0]));
else // Second group (operator) matched
result.push(nextPart[0]);
str = str.substring(nextPart.index+nextPart[0].length);
}
return result
}
function isOperator(char) {
return char === '*' || char === '/' || char === '^' || char === '+' || char === '-';
}
function Polynomial(value) {
this.terms = (value!==undefined) ? [new Term(value)] : [];
}
Polynomial.prototype.simplify = function() {
for (var i=0; i<this.terms.length-1; i++) {
if (this.terms[i].coeff === 0) {
this.terms.splice(i--, 1);
continue;
}
for (var j=i+1; j<this.terms.length; j++) {
if (Term.same(this.terms[i], this.terms[j])) {
this.terms[i] = Term.add(this.terms[i], this.terms[j]);
this.terms.splice(j--, 1);
}
}
}
}
Polynomial.add = function(a, b) {
var result = new Polynomial();
result.terms = a.terms.concat(b.terms);
result.simplify();
return result
}
Polynomial.multiply = function(a, b) {
var result = new Polynomial();
a.terms.forEach(function(aTerm) {
b.terms.forEach(function (bTerm) {
result.terms.push(Term.multiply(aTerm, bTerm));
});
});
result.simplify();
return result
}
Polynomial.prototype.toHtml = function() {
var html = ''
for (var i=0; i<this.terms.length; i++) {
var term = this.terms[i];
if (i !== 0)
html += (term.coeff < 0) ? ' - ' : ' + ';
else
html += (term.coeff < 0) ? '-' : '';
var coeff = Math.abs(term.coeff);
html += (coeff === 1 && Object.keys(term.symbols).length > 0) ? '' : coeff;
for (var symbol in term.symbols) {
var exp = term.symbols[symbol];
exp = (exp !== 1) ? exp : '';
html += symbol + '<sup>' + exp + '</sup>';
}
}
return html;
}
function Term(value) {
this.symbols = {};
if (typeof value==='string') { // Symbol
this.symbols[value] = 1;
this.coeff = 1;
} else if (typeof value==='number') { // Number
this.coeff = value;
} else {
this.coeff = 1;
}
}
Term.same = function(a, b) {
if (Object.keys(a.symbols).length != Object.keys(b.symbols).length)
return false
else
for (var aSymbol in a.symbols)
if (a.symbols[aSymbol] != b.symbols[aSymbol]) return false
return true
}
Term.add = function(a, b) {
var result = new Term();
Object.assign(result.symbols, a.symbols);
result.coeff = a.coeff + b.coeff;
return result
}
Term.multiply = function(a, b) {
var result = new Term();
Object.assign(result.symbols, a.symbols);
for (var symbol in b.symbols) {
if (!(symbol in result.symbols))
result.symbols[symbol] = 0;
result.symbols[symbol] += b.symbols[symbol];
if (result.symbols[symbol] === 0)
delete result.symbols[symbol];
}
result.coeff = a.coeff * b.coeff;
return result
}
function expand(str) {
var result = [];
var parens = findOuterParens(str);
while (parens) {
result = result.concat(parseExpressionStr(str.slice(0,parens.start)));
result.push(expand(str.slice(parens.start+1, parens.end)))
str = str.slice(parens.end+1);
parens = findOuterParens(str);
}
result = result.concat(parseExpressionStr(str));
// Move -s to coefficients
var minus = result.indexOf('-'), minusPoly = new Polynomial(-1);
while (minus !== -1) {
result[minus] = '+';
result[minus+1] = Polynomial.multiply(minusPoly, result[minus+1]);
minus = result.indexOf('-');
}
// Get rid of +s that follow another operator
var plus = result.indexOf('+');
while (plus !== -1) {
if (plus===0 || isOperator(result[plus-1])) {
result.splice(plus--, 1);
}
plus = result.indexOf('+', plus+1);
}
// Convert /s to *s
var divide = result.indexOf('/');
while (divide !== -1) {
result[divide] = '*';
var termsToInvert = result[divide+1].terms;
if (termsToInvert.length > 1)
throw Error('Attempt to divide by a polynomial with more than one term.');
var termToInvert = termsToInvert[0];
for (var symbol in termToInvert.symbols) {
termToInvert.symbols[symbol] = -termToInvert.symbols[symbol];
}
termToInvert.coeff = 1/termToInvert.coeff;
divide = result.indexOf('/');
}
// Convert ^s to *s
var power = result.indexOf('^');
while (power !== -1) {
var exp = result[power+1];
if (exp.terms.length > 1 || Object.keys(exp.terms[0].symbols).length != 0)
throw Error('Attempt to use non-number as an exponent');
exp = exp.terms[0].coeff;
var base = result[power-1];
var expanded = [power-1, 3, base];
for (var i=0; i<exp-1; i++) {
expanded.push('*');
expanded.push(base);
}
result.splice.apply(result, expanded);
power = result.indexOf('^');
}
// Add implicit *s
for (var i=0; i<result.length-1; i++)
if (!isOperator(result[i]) && !(isOperator(result[i+1])))
result.splice(i+1, 0, '*');
// Multiply
var mult = result.indexOf('*');
while (mult !== -1) {
var product = Polynomial.multiply(result[mult-1], result[mult+1]);
result.splice(mult-1, 3, product);
mult = result.indexOf('*');
}
// Add
var add = result.indexOf('+');
while (add !== -1) {
var sum = Polynomial.add(result[add-1], result[add+1]);
result.splice(add-1, 3, sum);
add = result.indexOf('+');
}
result[0].simplify();
return result[0];
}
var problems = ['(x+1)(x+1)/x', '(x+1)^3', '(x^2*x)(x^2)', '(x+1)(x+1)(x+1)',
'(x+1)^2', 'x(x+1)', '1x^4', '(x + (x+2))(x+5)', '3x^0', '2^3',
'(x+2x(x+2(x+1)x))', '(x+1)(x-1)', '(x+1)(y+1)', '(x+y+t)(q+x+7)'];
var solutionHTML = '';
for (var i = 0; i<problems.length; i++) {
solutionHTML += problems[i] + ' => ' + expand(problems[i]).toHtml() + '<br>';
}
document.body.innerHTML = solutionHTML;
</script>
</html>
It outputs:
I developed a plugin and when I call the plugin getting an error like Uncaught TypeError: Cannot read property 'convert' of undefined.
Here is my Plugin ,Its not working when I calling in my scripts
( function ($) {
$.siPrifixx = function(element, options) {
var defaults = {
foo: 'bar',
onFoo: function() {
}
}
var plugin = this;
plugin.settings = {
maxDigits: 8,
seperator: true,
decimal: 1,
popUp: false,
countUp:false
}
var $element = $(element),
element = element;
plugin.init = function() {
var value =$(element);
console.log(value);
plugin.settings = $.extend({
}, defaults, options);
var maxDigits = plugin.settings.maxDigits;
console.log(defaults);
if (typeof value === 'string') {
var parts = value.split(",");
var num = parts.join("");
var isNumber = regIsNumber(num)
if(isNumber){
var number = (parseInt(num));
}else{
number = num;
}
}else if (typeof value === 'number'){
number = value
}
var data_max = $(this).attr('data-max-digit');
if(typeof data_max !== 'undefined'){
maxDigits = data_max;
}
var checkNumber = typeof number !== 'undefined' && !isNaN(number) && Math.round(number).toString().length > maxDigits;
if (plugin.settings.popUp && checkNumber) {
$(this).addClass('tooltip', value);
var tootip = $(this).tooltipster({
theme: 'tooltipster-default',
functionInit: function () {
return value
}
})
if(!tootip)
console.log("We couldn't find tooltipster function.Please make sure you have loaded the plugin")
}
if (plugin.settings.countUp && (Math.round(value).toString().length <= maxDigits)) {
var cUp = new countUp(
plugin.settings.countUp, 0, Number(value), 0, 1, null);
cUp.start();
if(!cUp)
console.log("We couldn't find counter function.Please make sure you have loaded the plugin")
}
if (checkNumber) {
var results = plugin.convert(number);
$(this).html(results);
} else {
if (plugin.settings.seperator) {
var cvalue = numberWithCommas(value)
$(this).html(cvalue)
} else {
$(this).html(value)
}
if(typeof value === 'string')
if(checkDate(value)){
$(this).html(value)
}
}
}
plugin.convert = function(number){
var n = settings.decimal
var decPlace = Math.pow(10, n);
var abbrev = ["K", "M", "B", "T"];
for (var i = abbrev.length - 1; i >= 0; i--) {
var size = Math.pow(10, (i + 1) * 3);
if (size <= number) {
number = Math.round(number * decPlace / size) / decPlace;
if ((number == 1000) && (i < abbrev.length - 1)) {
number = 1;
i++;
}
number += abbrev[i];
break;
}
}
console.log(number);
return number;
}
plugin.init();
//use to convert numbers with comma seperated
}
$.fn.siPrifixx = function (options) {
return this.each(function() {
if (undefined == $(this).data('siPrifixx')) {
var plugin = new $.siPrifixx(this,options);
$(this).data('siPrifixx', plugin);
}
});
};
}(jQuery));
I use to call the plugin by $(this).data('siPrifixx').convert(value);});
What is the problem with my code?How can I modify my plugin to gets works?
How can I call convert method in code.
One approach would be to divide plugin into individual portion which each return expected result, then merge the discrete working portions one by one until the full plugin in functional
(function($) {
var settings = {
maxDigits: 8,
seperator: true,
decimal: 0,
popUp: false,
countUp: false
}
function convert(number, options) {
var opts = $.extend(settings, options || {});
var n = opts.decimal;
console.log(opts);
var decPlace = Math.pow(10, n);
var abbrev = ["K", "M", "B", "T"];
for (var i = abbrev.length - 1; i >= 0; i--) {
var size = Math.pow(10, (i + 1) * 3);
if (size <= number) {
number = Math.round(number * decPlace / size) / decPlace;
if ((number == 1000) && (i < abbrev.length - 1)) {
number = 1;
i++;
}
number += abbrev[i];
break;
}
}
this.data("number", number); // set `number` at `.data("number")`
return this; // return `this` for chaining jQuery methods
}
$.fn.convert = convert;
}(jQuery));
var div = $("div");
div.convert(1500000, {decimal:1});
console.log(div.data("number"))
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div></div>
You should call it like this:
$(this).data('siPrifixx').plugin.convert(value);});
I'm making a system that will use a calculator, however, at any given time the user must click on a word, and that word needs to have a value, for example 20. see the example of how mathematical formula works:
car = 20;
2 + (car + 1);
the result of this formula is 23
these words and values comes from database
Anyone know how to do this in javascript?
the javascript code:
function addChar(input, character) {
if (input.value == null || input.value == "0"){
input.value = character;
}
else{
input.value += character;
}
}
function cos(form) {
form.display.value = Math.cos(form.display.value);
}
function sin(form) {
form.display.value = Math.sin(form.display.value);
}
function tan(form) {
form.display.value = Math.tan(form.display.value);
}
function sqrt(form) {
form.display.value = Math.sqrt(form.display.value);
}
function ln(form) {
form.display.value = Math.log(form.display.value);
}
function exp(form) {
form.display.value = Math.exp(form.display.value);
}
function sqrt(form) {
form.display.value = Math.sqrt(form.display.value);
}
function deleteChar(input) {
input.value = input.value.substring(0, input.value.length - 1)
}
function changeSign(input) {
if (input.value.substring(0, 1) == "-"){
input.value = input.value.substring(1, input.value.length);
}
else{
input.value = "-" + input.value
}
}
function compute(form) {
form.display.value = eval(form.display.value)
}
function square(form) {
form.display.value = eval(form.display.value) *
eval(form.display.value)
}
var data = {"car":20};
var formula = " 2 + (%car% + 1)";
for (var index in data){
formula = formula.replace(new RegExp("%"+index+"%","g"),data[index]);
}
alert(eval(formula));
use prefix and suffix for ignoring partial match word replacing error.
i used %
How can I convert one date format to another format in JavaScript?
Example:
the old format is
YYYY/MM/DD
but I want to convert it into
DD-MM-YYYY
I think you can use jQuery UI library's datepicker: use the parseDate method to convert a string to a Date object, and then formatDate to convert the Date object to another string. Check the samples provided on the site; they include format modifiers.
Here -
// Utility function to append a 0 to single-digit numbers
Date.LZ = function(x) {return(x<0||x>9?"":"0")+x};
// Full month names. Change this for local month names
Date.monthNames = new Array('January','February','March','April','May','June','July','August','September','October','November','December');
// Month abbreviations. Change this for local month names
Date.monthAbbreviations = new Array('Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec');
// Full day names. Change this for local month names
Date.dayNames = new Array('Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday');
// Day abbreviations. Change this for local month names
Date.dayAbbreviations = new Array('Sun','Mon','Tue','Wed','Thu','Fri','Sat');
// Used for parsing ambiguous dates like 1/2/2000 - default to preferring 'American' format meaning Jan 2.
// Set to false to prefer 'European' format meaning Feb 1
Date.preferAmericanFormat = true;
// If the getFullYear() method is not defined, create it
if (!Date.prototype.getFullYear) {
Date.prototype.getFullYear = function() { var yy=this.getYear(); return (yy<1900?yy+1900:yy); } ;
}
// Parse a string and convert it to a Date object.
// If no format is passed, try a list of common formats.
// If string cannot be parsed, return null.
// Avoids regular expressions to be more portable.
Date.parseString = function(val, format) {
// If no format is specified, try a few common formats
if (typeof(format)=="undefined" || format==null || format=="") {
var generalFormats=new Array('y-M-d','MMM d, y','MMM d,y','y-MMM-d','d-MMM-y','MMM d','MMM-d','d-MMM');
var monthFirst=new Array('M/d/y','M-d-y','M.d.y','M/d','M-d');
var dateFirst =new Array('d/M/y','d-M-y','d.M.y','d/M','d-M');
var checkList=new Array(generalFormats,Date.preferAmericanFormat?monthFirst:dateFirst,Date.preferAmericanFormat?dateFirst:monthFirst);
for (var i=0; i<checkList.length; i++) {
var l=checkList[i];
for (var j=0; j<l.length; j++) {
var d=Date.parseString(val,l[j]);
if (d!=null) {
return d;
}
}
}
return null;
};
this.isInteger = function(val) {
for (var i=0; i < val.length; i++) {
if ("1234567890".indexOf(val.charAt(i))==-1) {
return false;
}
}
return true;
};
this.getInt = function(str,i,minlength,maxlength) {
for (var x=maxlength; x>=minlength; x--) {
var token=str.substring(i,i+x);
if (token.length < minlength) {
return null;
}
if (this.isInteger(token)) {
return token;
}
}
return null;
};
val=val+"";
format=format+"";
var i_val=0;
var i_format=0;
var c="";
var token="";
var token2="";
var x,y;
var year=new Date().getFullYear();
var month=1;
var date=1;
var hh=0;
var mm=0;
var ss=0;
var ampm="";
while (i_format < format.length) {
// Get next token from format string
c=format.charAt(i_format);
token="";
while ((format.charAt(i_format)==c) && (i_format < format.length)) {
token += format.charAt(i_format++);
}
// Extract contents of value based on format token
if (token=="yyyy" || token=="yy" || token=="y") {
if (token=="yyyy") {
x=4;y=4;
}
if (token=="yy") {
x=2;y=2;
}
if (token=="y") {
x=2;y=4;
}
year=this.getInt(val,i_val,x,y);
if (year==null) {
return null;
}
i_val += year.length;
if (year.length==2) {
if (year > 70) {
year=1900+(year-0);
}
else {
year=2000+(year-0);
}
}
}
else if (token=="MMM" || token=="NNN"){
month=0;
var names = (token=="MMM"?(Date.monthNames.concat(Date.monthAbbreviations)):Date.monthAbbreviations);
for (var i=0; i<names.length; i++) {
var month_name=names[i];
if (val.substring(i_val,i_val+month_name.length).toLowerCase()==month_name.toLowerCase()) {
month=(i%12)+1;
i_val += month_name.length;
break;
}
}
if ((month < 1)||(month>12)){
return null;
}
}
else if (token=="EE"||token=="E"){
var names = (token=="EE"?Date.dayNames:Date.dayAbbreviations);
for (var i=0; i<names.length; i++) {
var day_name=names[i];
if (val.substring(i_val,i_val+day_name.length).toLowerCase()==day_name.toLowerCase()) {
i_val += day_name.length;
break;
}
}
}
else if (token=="MM"||token=="M") {
month=this.getInt(val,i_val,token.length,2);
if(month==null||(month<1)||(month>12)){
return null;
}
i_val+=month.length;
}
else if (token=="dd"||token=="d") {
date=this.getInt(val,i_val,token.length,2);
if(date==null||(date<1)||(date>31)){
return null;
}
i_val+=date.length;
}
else if (token=="hh"||token=="h") {
hh=this.getInt(val,i_val,token.length,2);
if(hh==null||(hh<1)||(hh>12)){
return null;
}
i_val+=hh.length;
}
else if (token=="HH"||token=="H") {
hh=this.getInt(val,i_val,token.length,2);
if(hh==null||(hh<0)||(hh>23)){
return null;
}
i_val+=hh.length;
}
else if (token=="KK"||token=="K") {
hh=this.getInt(val,i_val,token.length,2);
if(hh==null||(hh<0)||(hh>11)){
return null;
}
i_val+=hh.length;
hh++;
}
else if (token=="kk"||token=="k") {
hh=this.getInt(val,i_val,token.length,2);
if(hh==null||(hh<1)||(hh>24)){
return null;
}
i_val+=hh.length;
hh--;
}
else if (token=="mm"||token=="m") {
mm=this.getInt(val,i_val,token.length,2);
if(mm==null||(mm<0)||(mm>59)){
return null;
}
i_val+=mm.length;
}
else if (token=="ss"||token=="s") {
ss=this.getInt(val,i_val,token.length,2);
if(ss==null||(ss<0)||(ss>59)){
return null;
}
i_val+=ss.length;
}
else if (token=="a") {
if (val.substring(i_val,i_val+2).toLowerCase()=="am") {
ampm="AM";
}
else if (val.substring(i_val,i_val+2).toLowerCase()=="pm") {
ampm="PM";
}
else {
return null;
}
i_val+=2;
}
else {
if (val.substring(i_val,i_val+token.length)!=token) {
return null;
}
else {
i_val+=token.length;
}
}
}
// If there are any trailing characters left in the value, it doesn't match
if (i_val != val.length) {
return null;
}
// Is date valid for month?
if (month==2) {
// Check for leap year
if ( ( (year%4==0)&&(year%100 != 0) ) || (year%400==0) ) { // leap year
if (date > 29){
return null;
}
}
else {
if (date > 28) {
return null;
}
}
}
if ((month==4)||(month==6)||(month==9)||(month==11)) {
if (date > 30) {
return null;
}
}
// Correct hours value
if (hh<12 && ampm=="PM") {
hh=hh-0+12;
}
else if (hh>11 && ampm=="AM") {
hh-=12;
}
return new Date(year,month-1,date,hh,mm,ss);
};
// Check if a date string is valid
Date.isValid = function(val,format) {
return (Date.parseString(val,format) != null);
};
// Check if a date object is before another date object
Date.prototype.isBefore = function(date2) {
if (date2==null) {
return false;
}
return (this.getTime()<date2.getTime());
};
// Check if a date object is after another date object
Date.prototype.isAfter = function(date2) {
if (date2==null) {
return false;
}
return (this.getTime()>date2.getTime());
};
// Check if two date objects have equal dates and times
Date.prototype.equals = function(date2) {
if (date2==null) {
return false;
}
return (this.getTime()==date2.getTime());
};
// Check if two date objects have equal dates, disregarding times
Date.prototype.equalsIgnoreTime = function(date2) {
if (date2==null) {
return false;
}
var d1 = new Date(this.getTime()).clearTime();
var d2 = new Date(date2.getTime()).clearTime();
return (d1.getTime()==d2.getTime());
};
// Format a date into a string using a given format string
Date.prototype.format = function(format) {
format=format+"";
var result="";
var i_format=0;
var c="";
var token="";
var y=this.getYear()+"";
var M=this.getMonth()+1;
var d=this.getDate();
var E=this.getDay();
var H=this.getHours();
var m=this.getMinutes();
var s=this.getSeconds();
var yyyy,yy,MMM,MM,dd,hh,h,mm,ss,ampm,HH,H,KK,K,kk,k;
// Convert real date parts into formatted versions
var value=new Object();
if (y.length < 4) {
y=""+(+y+1900);
}
value["y"]=""+y;
value["yyyy"]=y;
value["yy"]=y.substring(2,4);
value["M"]=M;
value["MM"]=Date.LZ(M);
value["MMM"]=Date.monthNames[M-1];
value["NNN"]=Date.monthAbbreviations[M-1];
value["d"]=d;
value["dd"]=Date.LZ(d);
value["E"]=Date.dayAbbreviations[E];
value["EE"]=Date.dayNames[E];
value["H"]=H;
value["HH"]=Date.LZ(H);
if (H==0){
value["h"]=12;
}
else if (H>12){
value["h"]=H-12;
}
else {
value["h"]=H;
}
value["hh"]=Date.LZ(value["h"]);
value["K"]=value["h"]-1;
value["k"]=value["H"]+1;
value["KK"]=Date.LZ(value["K"]);
value["kk"]=Date.LZ(value["k"]);
if (H > 11) {
value["a"]="PM";
}
else {
value["a"]="AM";
}
value["m"]=m;
value["mm"]=Date.LZ(m);
value["s"]=s;
value["ss"]=Date.LZ(s);
while (i_format < format.length) {
c=format.charAt(i_format);
token="";
while ((format.charAt(i_format)==c) && (i_format < format.length)) {
token += format.charAt(i_format++);
}
if (typeof(value[token])!="undefined") {
result=result + value[token];
}
else {
result=result + token;
}
}
return result;
};
// Get the full name of the day for a date
Date.prototype.getDayName = function() {
return Date.dayNames[this.getDay()];
};
// Get the abbreviation of the day for a date
Date.prototype.getDayAbbreviation = function() {
return Date.dayAbbreviations[this.getDay()];
};
// Get the full name of the month for a date
Date.prototype.getMonthName = function() {
return Date.monthNames[this.getMonth()];
};
// Get the abbreviation of the month for a date
Date.prototype.getMonthAbbreviation = function() {
return Date.monthAbbreviations[this.getMonth()];
};
// Clear all time information in a date object
Date.prototype.clearTime = function() {
this.setHours(0);
this.setMinutes(0);
this.setSeconds(0);
this.setMilliseconds(0);
return this;
};
// Add an amount of time to a date. Negative numbers can be passed to subtract time.
Date.prototype.add = function(interval, number) {
if (typeof(interval)=="undefined" || interval==null || typeof(number)=="undefined" || number==null) {
return this;
}
number = +number;
if (interval=='y') { // year
this.setFullYear(this.getFullYear()+number);
}
else if (interval=='M') { // Month
this.setMonth(this.getMonth()+number);
}
else if (interval=='d') { // Day
this.setDate(this.getDate()+number);
}
else if (interval=='w') { // Weekday
var step = (number>0)?1:-1;
while (number!=0) {
this.add('d',step);
while(this.getDay()==0 || this.getDay()==6) {
this.add('d',step);
}
number -= step;
}
}
else if (interval=='h') { // Hour
this.setHours(this.getHours() + number);
}
else if (interval=='m') { // Minute
this.setMinutes(this.getMinutes() + number);
}
else if (interval=='s') { // Second
this.setSeconds(this.getSeconds() + number);
}
return this;
};
Copy this to a .js file, and include it in your page.
Then you can use the format() method on the Date object.
You can also find another library here.
My date extensions will do that well - they also parses data formats and does a lot of date math/compares as well:
DP_DateExtensions Library
Not sure if it'll help, but I've found it invaluable in several projects. The date functions are (mostly) based on CFML (if that matters).
I'm not saying that they're better than the other options given - but I am proud of them and it never (well... almost never) hurts to be spoilt for choice.
If you don't use jQuery (and I can't think why, but just in case), I have created a patch for the Javascript Date object which will allow you to both parse dates from strings in different formats and convert dates to strings in different formats.
You can see more info on Javascript Date Formatter article on my blog.
My answer is very late but I think following solution is simple and effective for this question. This works for me always.
Here you go :
function dateToYMD(date) {
var d = date.getDate();
var m = date.getMonth() + 1;
var y = date.getFullYear();
return ''+ (d <= 9 ? '0' + d : d) + '-' + (m<=9 ? '0' + m : m) + '-' + y ;
}