Develop Reference

JavasScript Add half a percent to a number any amount of times I choose

Hi I need a block of code for some math that I'm trying to work out. The code I'm looking for will be able to add half a percent (0.005) to a number and return the result back to me. I need the code to take two separate inputs, the first is the start number, and the second is how many times I want the loop to execute. An example would be if I started with 7000 the code should output ~7321.37 (if possible let it stop after 2 decimal points). Thank you for the help in advance!
Code example of what I'm trying to do:
function growth(initialValue, timesOfExecution)` {
let answer;
let execute;
while (execute > 0) {
answer = initialValue + initialValue(0.05)
execute--
}
return answer;
}
console.log(growth(7000, 9))

Here you go:
function growth(initialValue, timesOfExecution) {
for (let i = 0; i < timesOfExecution; i++) {
initialValue = initialValue + (initialValue * 0.005)
}
return initialValue.toFixed(2);
}
console.log(growth(7000, 9))

How to use .toFixed() (or any alternative) on Nerdamer.solve solutions?

I'm using Nerdamer.solve() to get some linear equation roots. It's working fine but I wonder if there is any way to get only the first 4 decimals of every solution.
EquationSolver.js
//First step, using Nerdamer to solve the equation stored in value
sol_raw = this.nerdamer.solve(value,'x');
xs = this.nerdamer(sol_raw.toString());
//Second step, using Function() in order to evaluate the solutions
solution= Function('return ' + this.nerdamer(xs).evaluate().toString())()
At this point, I'm getting correct results like: 1.74343434. Since I'm rendering the results using Katex, I would like to know where to implement .toFixed(4) or any pseudo way (maybe a Nerdamer method to use n number of decimals on .evaluate()?).
Note.
The result (solution) is a string like [1.74343434, 0.434343, ...] so I could transform it into a float variable and then use .toFixed() but this not an easy solution because the number of roots depends on the equation's grade.
Nerdamer's documentation about evaluate: documentation

#CoronelV,
Another possible approach is to create a toFixed function for formatting the numbers which would take into account real and complex solutions and then calling it on your solutions. Here's a more generalized approach.
var toFixed = function(value, n) {
var img = Number(nerdamer.imagpart(value).text()).toFixed(n);
var real = Number(nerdamer.realpart(value).text()).toFixed(n);
// Format the number assuming i denotes imaginary in your case
var formatted = '';
if(real !== '0.0000') {
formatted += real;
}
if(img !== '0.0000') {
// Put the plus sign betweent the real and imaginary
if(img.charAt(0) !== '-' && formatted) {
formatted += '+';
}
// Assuming you're using i and not j for instance
formatted += img+'i';
}
return formatted;
};
So in your case this would be become something like:
sol_raw = this.nerdamer.solve(value,'x');
xs = this.nerdamer(sol_raw.toString()).each(function(solution) {
roundedSolutions.push(toFixed(solution, 4));
});
this.setState({
solution: roundedSolution.join(''),
equation:value})
This would possibly eliminate the need for your try catch block.

Since the solution is rendered using KaTeX, it's possible rounding the solution via Latex's package, but its even simplest taking the suggestion of #Dj Burb.
Here is my approach:
try {
sol_raw = this.nerdamer.solve(value,'x');
xs = this.nerdamer(sol_raw.toString());
Function('return '+ this.nerdamer(xs).evaluate().toString())().forEach(element => {
roundedSolution.push(element.toFixed(4)) });
} catch (e) {
}
this.setState({
solution: roundedSolution.join(''),
equation:value})
The use of try catch is imperative because while writing the equation, solution.toFixed() returns an error.

Javascript - How to know how much string matched in another string?

I have been implementing a simple quiz for English. In that, we need to validate answers, which are entered by users in input field. In the current implementation, I am comparing the correct answer with user's answer exactly. Like,
HTML
<input type="text" id="answer" />
<button onclick="validate()">Validate</button>
Javascript
var question = "Do you like movies?",
answer = "No, I don't like movies.";
function validate() {
var userInput = document.getElementById('answer').value;
if(answer == userInput) {
console.log("correct");
} else {
console.log("wrong");
}
}
But I don't want validate exactly. Like, ignore case sensitive, commas, apostrophe, etc. For example if user enters,
i dont like movies
The answer can be correct. I don't know how start and where to start. Anyone please help.

One option would be to strip out all non-word characters and spaces, and compare the lower-case version of each replaced string:
var question = "Do you like movies?",
answer = "No, I don't like movies.";
const normalize = str => str
.replace(/[^\w ]/g, '')
.toLowerCase();
function validate(userInput) {
const noramlizedInput = normalize(userInput)
const noramlizedAnswer = normalize(answer);
if (noramlizedInput == noramlizedAnswer) {
console.log("correct");
} else {
console.log("wrong");
}
}
validate('No i dont like movies');
validate("NO!!!!! I DON''t like movies.");
Another option would be to loop through all possible substrings of the userInput and figure out which has the most overlap with the desired answer, but that's a whole lot more complicated.
An easier option would be to check to see how many overlapping words there are:
var question = "Do you like movies?",
answer = "No, I don't like movies.";
const normalize = str => str
.replace(/[^\w ]/g, '')
.toLowerCase()
.split(/\s+/)
function validate(userInput) {
const noramlizedInputArr = normalize(userInput);
const noramlizedAnswerArr = normalize(answer);
const overlapCount = noramlizedInputArr.reduce((a, word) => (
a + Number(noramlizedAnswerArr.includes(word))
), 0);
console.log(overlapCount);
if (overlapCount >= 4) {
console.log("correct");
} else {
console.log("wrong");
}
}
validate('No i dont like movies');
validate("NO!!!!! I DON''t like movies.");
validate("i dont like movies.");
validate("Yes I like movies.");

If you are interested in simply catching spelling errors and small variations, a standard metric is called edit distance or Levenshtein distance. This is a count of the minimum number of deletions, insertions, or substitutions you need to change one text into another. Strings like "No I don't like the movies" and "No I don't like the moveys" will have small edit distances.
Here's a quick and dirty recursive edit distance function that will give you an idea:
function validate(text, pattern) {
// some simple preprocessing
let p = pattern.toLowerCase().replace(/[^a-z]+/ig, '')
let t= text.toLowerCase().replace(/[^a-z]+/ig, '')
// memoize recursive algorithm
let matrix = Array.from({length: t.length + 1}, () => [])
function editDistance(text, pattern, i = 0, j = 0){
if(i == text.length && j == pattern.length) return 0
if(i == text.length) return pattern.length - j
if(j == pattern.length) return text.length - i
let choices = [
(matrix[i+1][j+1] || (matrix[i+1][j+1] = editDistance(text, pattern, i+1, j+1))) + (text[i].toLowerCase() === pattern[j].toLowerCase() ? 0 : 1),
(matrix[i+1][j] || (matrix[i+1][j] = editDistance(text, pattern, i+1, j))) + 1,
(matrix[i][j+1] || (matrix[i][j+1] = editDistance(text, pattern, i, j+1))) + 1
]
return Math.min(...choices)
}
return editDistance(t, p)
}
// similar strings have smaller edit distances
console.log(validate("No I dont lik moves","No i dont like movies"))
// a little less similar
console.log(validate("Yes I like movies","No i dont like movies"))
// totally different
console.log(validate("Where is the bathroom","No i dont like movies"))
// careful -- small edit distance !== close meaning
console.log(validate("I do like tacos","I don't like tacos"))
Picking a minimum acceptable distance works pretty well for matching strings with small typos. Of course, if you are trying to gauge user intent, none of these simple hues tics will work. Strings like "I love tacos" and "I loath tacos" have a small edit distance and you can't tell that they mean the opposite without knowledge of the language. If you need to do this level of checking you can try using a service like Watson Conversation that will return user intents to input.

remove all Decimals and single numbers from array / string

so my script generates a big blob of "Piano Notes" which are similar to...
var songNotes = "...";
the large Piano notes content
and my problem is between the piano notes which i need [also in the fiddle] there are empty ",," and decimal numbers.. so i cant figure out how to remove the empty
,, and decimals as big as
"1.0416666666642413,0.625,0,g3,1498.9583333333358,,0,c3,1.0416666666642413,0.625,0,c3"
and i want them removed except the the needed words which are
var theRightOnes = "s2,as2,cs3,ds3,fs3,gs3,as3,gs3,cs4,ds4,fs4,cs3,as4,gs4,ds5,a2,cs4,b2,c3,a3,ds4,b3,c4,as3,gs2,e3,c3,c4,cs3,ds3,a4,fs3,gs3,as3,g3,f3,b4,c5,a3,d4,as2,e4,g4,d3,b3,b2,f4,a2,d4,e4,cs5,gs1,e2,c2,c3,cs2,ds2,a3,fs2,gs2,as2,g2,f2,b3,c4,a2,d3,as1,e3,g3,d2,b2,b1,f3,a1,d5,e5";
so can anyone give me a clue on how this can be accomplished?
if anyone needs more info then i am ready oblige to do so..
Regards - Adarsh Hegde

var notesArr = songNotes.split(",");
var len = notesArr.length;
while(len--) {
if(!notesArr[len] || !isNaN(parseInt(notesArr[len], 10))) {
notesArr.splice(len, 1);
}
}
songNotes = notesArr.join(",");

I think you want to remove all the numbers from notes.
You can say like bellow
var notes = songNotes.split(",").filter(function(note){
return isNaN(note);
});
console.log(notes);

You can use Array.filter (see MDN) to weed out unwanted values:
var wantedNotes = songNotes.split(',')
.filter(function (v) {
return isNaN(+v) && v.trim().length
});
jsFiddle

just use regular expression,like this:
var a = "1.0416666666642413,0.625,0,g3,1498.9583333333358,,0,c3,1.0416666666642413,0.625,0,c3";
console.log(a.replace(/\b(\d+(\.\d+)?),+/g,""));

Javascript - Format number to always show the original decimal places

I need a js function that show the original count of decimals in a number. For example:
value display
2.31 2
1.0 1
2.3500 4
The problem is that i dont know how get the count of decimals.
I have that code:
value=2.3500;
return CountofDecimals(value); // must be display 4:
Anything help??? Thanks :P

That's not possible. There's no difference between the number 3.5 and 3.50 in JavaScript, or indeed in any other common programming language.
If you actually mean they're strings (value = '2.3500' rather than value = 2.3500) then you can use indexOf:
var decimalPlaces = value.length - value.indexOf('.') - 1;

Caveat: I hate this answer, I don't really advocate it
Don't store it as a number, store it as a string. This can result in "stringly typed" code quickly so it is inadvisable. It is a workaround since JavaScript uses a float as the number type.
Alternatively store it as an Object and parse out the format via a function call:
{ value = "1.2345", decimal = 4}
and use that to create the correct number format. If I had the requirement this is probably the hack I'd use. Or, I would have my server return the formatted string as you can pull that off easily server side.

If it would be possible take these numbers as strings, it definitely is possible..And quite simple actually.
function countDecimals(string){
var delimiters = [",","."];
for(var i = 0; i<delimiters.length; i++){
if(string.indexOf(delimiters[i])==-1) continue;
else{
return string.substring(string.indexOf(delimiters[i])+1).length;
}
}
}

You could use this function:
function decimalplaces(number)
{
numberastring = number.toString(10);
decimalpoint = numberastring.indexOf(".");
if(decimalpoint == -1)
{
return 0;
}
else
{
return numberastring.length - decimalpoint - 1;
}
}