Develop Reference

Set the last number in a string to negative

I have a string with diffrent mathematical characters, and i want to make the last number negative/positive. Let's say the string is "100/5*30-60+333". The result i want is "100/5*30-60+(-333)", and i want to convert it back to positive ("100/5*30-60+333").
function posNeg() {
// hiddenText is a <input> element. This is not shown.
let n = hiddenText.value;
n.split('+');
n.split('-');
n.split('*');
n.split('/');
console.log(n);
}
What i get is the whole hiddenText.value, and not an array of all numbers. Any tips?

First, I'd match all of the basic math operators to get their order:
const operatorsArr = n.match(/\+|\-|\/|\*/g)
Then, split the string:
function posNeg() {
// hiddenText is a <input> element. This is not shown.
let n = hiddenText.value;
n = n.replace(/\+|\-|\/|\*/g, '|');
n = n.split('|');
console.log(n);
}
Then, you will have an array of numbers, in which you can mutate the last number easily:
n[n.lengh-1] *= -1;
Now we can combine the two arrays together:
let newArr;
for (let i = 0; i < n.length; i++) {
newArr.push(n[i]);
if (operatorsArr[i]) newArr.push(operatorsArr[i]);
}
At last, you can rejoin the array to create the new String with a seperator of your choosing. In this example I'm using a space:
newArr = newArr.join(' ')
Please let me know how that works out for you.

Let's say the string is "100/5*30-60+333". The result i want is
"100/5*30-60+(-333)", and i want to convert it back to positive
("100/5*30-60+333").
The following code does that:
let mathStr = '100/5*30-60+333';
console.log(mathStr);
let tokens = mathStr.split('+');
let index = tokens.length - 1;
let lastToken = tokens[index];
lastToken = '('.concat('-', lastToken, ')');
let newMathStr = tokens[0].concat('+', lastToken);
console.log(newMathStr); // 100/5*30-60+(-333)
console.log(mathStr); // 100/5*30-60+333
EDIT:
... and i want to convert it back to positive ("100/5*30-60+333").
One way is to declare mathStr (with the value "100/5*30-60+333") as a var at the beginning and reuse it, later as you need. Another way is to code as follows:
let str = "100/5*30-60+(-333)";
str = str.replace('(-', '').replace(')', '');
console.log(str); // 100/5*30-60+333

To get numbers You can use replace function and split check code bellow :
function posNeg() {
// hiddenText is a <input> element. This is not shown.
let n = "100/5*30-60+333";
n = n.replace('+','|+');
n = n.replace('-','|-');
n = n.replace('*','|*');
n = n.replace('/','|/');
n=n.split('|');console.log(n);
// to use any caracter from array use it in removeop like example
// if we have array (split return) have 100 5 30 60 333 we get 100 for example
// we need to make removeop(n[0]) and that reutrn 100;
// ok now to replace last value to negative in string you can just make
// var lastv=n[n.length-1];
// n[n.length-1] ='(-'+n[n.length-1])+')';
//var newstring=n.join('');
//n[n.length-1]=lastv;
//var oldstring=n.join('');
}
function removeop(stringop)
{
stringop = stringop.replace('+','');
stringop = stringop.replace('-','');
stringop = stringop.replace('*','');
stringop = stringop.replace('/','');
return stringop;
}

If you really need to add "()", then you can modify accordingly
<script>
function myConversion(){
var str = "100/5*30-60-333";
var p = str.lastIndexOf("+");
if(p>-1)
{
str = str.replaceAt(p,"-");
}
else
{
var n = str.lastIndexOf("-");
if(n>-1)
str = str.replaceAt(n,"+");
}
console.log(str);
}
String.prototype.replaceAt=function(index, replacement) {
return this.substr(0, index) + replacement+ this.substr(index + replacement.length);
}
</script>

Counting the frequency of elements in an array in JavaScript

how do I count the frequency of the elements in the array, I'm new to Javascript and completely lost, I have looked at other answers here but can't get them to work for me. Any help is much appreciated.
function getText() {
var userText;
userText = document.InputForm.MyTextBox.value; //get text as string
alphaOnly(userText);
}
function alphaOnly(userText) {
var nuText = userText;
//result = nuText.split("");
var alphaCheck = /[a-zA-Z]/g; //using RegExp create variable to have only alphabetic characters
var alphaResult = nuText.match(alphaCheck); //get object with only alphabetic matches from original string
alphaResult.sort();
var result = freqLet(alphaResult);
document.write(countlist);
}
function freqLet(alphaResult) {
count = 0;
countlist = {
alphaResult: count
};
for (i = 0; i < alphaResult.length; i++) {
if (alphaResult[i] in alphaResult)
count[i] ++;
}
return countlist;
}

To count frequencies you should use an object which properties correspond to the letters occurring in your input string.
Also before incrementing the value of the property you should previously check whether this property exists or not.
function freqLet (alphaResult) {
var count = {};
countlist = {alphaResult:count};
for (i = 0; i < alphaResult.length; i++) {
var character = alphaResult.charAt(i);
if (count[character]) {
count[character]++;
} else {
count[character] = 1;
}
}
return countlist;
}

If you can use a third party library, underscore.js provides a function "countBy" that does pretty much exactly what you want.
_.countBy(userText, function(character) {
return character;
});
This should return an associative array of characters in the collection mapped to a count.
Then you could filter the keys of that object to the limited character set you need, again, using underscore or whatever method you like.

Do as below:
var __arr = [6,7,1,2,3,3,4,5,5,5]
function __freq(__arr){
var a = [], b = [], prev
__arr.sort((a,b)=>{return a- b} )
for(let i = 0; i<__arr.length; i++){
if(__arr[i] !== prev){
a.push(__arr[i])
b.push(1)
}else{
b[b.length - 1]++
}
prev = __arr[i]
}
return [a , b]
}

Get the value for each control from a list of elements?

I'm struggling to get the input value from a control in JavaScript, and I think it may have something to do with the collection of controls I'm looping through.
My page consists of many input controls with decimals in them. I'm only interested in controls starting with the name 'txtinput', and I need to tally up the values in each one. However, when I do this with the code below, all I seem to be getting out is a JSON looking string for each element.
function TallyPoints() {
var eles = [];
var inputs = document.getElementsByTagName("input");
var total = 0;
for (var i = 0; i < inputs.length; i++) {
if (inputs[i].name.indexOf('txtpoints') == 0) {
total += document.getElementsByName(inputs[i].name)[0].value;
}
}
alert('Total: ' + total.toString());
};
What I end up with is a value that looks like this:
Total: 0{"enabled":false,"emptyMessage":"","validationText":"333.33","valueAsString":"333.33","minValue":-70368744177664,"maxValue":70368744177664,"lastSetTextBoxValue":"333.33"}{"enabled":false,"emptyMessage":"","validationText":"5.66","valueAsString":"5.66","minValue":-70368744177664,"maxValue":70368744177664,"lastSetTextBoxValue":"5.66"}
Any ideas?

You probably want parseFloat() so your addition works properly (fiddle):
var inputs = document.querySelectorAll("input[name^=txtpoints]");
var total = [].reduce.call(inputs, function (p, c) {
return p + (parseFloat(c.value) || 0);
}, 0);
See also parseInt(), isNaN(), and Array.prototype.reduce()

Try this:
function TallyPoints() {
var inputs = document.getElementsByTagName("input");
var total = 0;
for (var i = 0; i < inputs.length; i++) {
if (inputs[i].name.indexOf('txtpoints') == 0) {
var val = parseFloat(inputs[i].value);
if (!isNaN(val)) {
total += val;
}
}
}
alert('Total: ' + total);
};
parseFloat is needed to convert the input from a string to a number, so that + will do addition rather than concatenation. There's no need to use getElementsByName, since you already have the element in inputs[i]. There's no need to use total.toString(); concatenating a number to a string converts it automatically.
The if (!isNan(val)) test skips over the inputs that don't contain numbers.
You could also use document.querySelectorAll('input[name^=txtpoints]') to find the relevant input elements in one step.

Getting range from a list using regular expressions

I have a list of numbers such as
var list = ["123","12345678","123","234,2345","2.34567","123.12345","-123","-0.1234","-324215.45"];
This list can have negative, positive numbers with optional decimal values, also negative or positive.
I need to use regular expressions to do 3 things:
getAllNumbersBeforeValue(value);
getAllNumbersAfterValue(value);
getRangeBetweenValues(valueFrom, valueTo);
Value passed in is not known, could be any number.
Update 1:
I've got this, which isn't perfect but works on some numbers:
var a = function(rand) {
var val = "";
var numArr = rand.split("");
for(var i = 0; i < numArr.length; i++) {
val = val + (Number(numArr[i])+1);
}
return "^[^" + val.split("").join("-9][^") + "-9]$"
}; // outputs "^[^2-9][^3-9][^4-9][^5-9][^6-9]$" with rand "12345"
Im trying to get a regular expression programmatically generated from a given value
For example "123456" is a random number (rand), I would like to be able to filter an array of numbers for values that are higher then rand (or lower then rand) using a regex value.
Thanks

You could use underscore.js (http://underscorejs.org) to filter your results. For example...
var list = ["123","12345678","123","234,2345","2.34567","123.12345","-123","-0.1234","-324215.45"];
function getAllNumbersBeforeValue(list, value) {
return _.filter(list, function(num) {
return num < value;
});
}
Here's an example without using a framework...
function getAllNumbersBeforeValue(list, value) {
var output = [];
for(var i = 0; i < list.length; i++) {
if(list[i] < value) {
output.push(list[i]);
}
}
return output;
}
getAllNumbersBeforeValue(list, 123);

jQuery removing values from a comma separate list

Given an input like:
<input type="test" value="3,4,9" />
What's the best way to remove a value like 9, 4 or 3, without having issues with the commas, I don't want this ending up:
value="3,4,"
value="3,,9"
value=",4,9"
Is there a clean way to get this done in JavaScript/jQuery?

You could split your value into an array, then filter out values you do not want.
$("input[type='test']").val().split(",") // ["3","4","9"]
.filter(function(v){return !isNaN(parseInt(v))}) // filter out anything which is not 0 or more
Here is a less terse version which filters out anything which is not numeric
var array = $("input[type='test']").val().split(",");
// If you are dealing with numeric values then you will want
// to cast the string as a number
var numbers = array.map(function(v){ return parseInt(v)});
// Remove anything which is not a number
var filtered = numbers.filter(function(v){ return !isNaN(v)});
// If you want to rejoin your values
var joined = filtered.join(",");
Finally change the value on the input
$("input[type='test']").val(joined);

Similar to PHP implode/explode functions
Array.prototype.remove = function(from, to) {
var rest = this.slice((to || from) + 1 || this.length);
this.length = from < 0 ? this.length + from : from;
return this.push.apply(this, rest);
};
var explode = value.split(',');
explode.remove(1);
var implode = explode.join(',');
Documentation:
fce: Split
fce: Join
fce: Array.remove

No jQuery required :P
<script type="text/javascript">
//var subject = '3,4,9';
//var subject = '3,,9';
var subject = ',,4,9';
var clean = Array();
var i = 0;
subject = subject.split(',');
for (var a in subject)
{
if(subject[a].length)
{
clean[i] = subject[a];
i++;
}
}
document.write(clean.join(','));
</script>

You may also use pure javascript. Let say you want to take off only "4":
value = value.replace(/4,?/, '')
or "3" and "9":
value = value.replace(/([39],?)+/, '')

I think this function will work for what you are trying to do: http://www.w3schools.com/jsref/jsref_split.asp
string.split(separator, limit)

use
array = string.split(separator);
to break a string into an array. then use this to join after manipulations.
string = array.join(separator);

var ary = value.split(',');
ary.splice(indexOfItemToRemove,1)
var result = ary.join(',');

This is discussed in another post:
remove value from comma separated values string
var removeValue = function(list, value, separator) {
separator = separator || ",";
var values = list.split(",");
for(var i = 0 ; i < values.length ; i++) {
if(values[i] == value) {
values.splice(i, 1);
return values.join(",");
}
}
return list;
}

You can use this function:
function removeComma(x) {
var str = '';
var subs = '';
for(i=1; i<=x.length; i++) {
subs = x.substring(i-1, i).trim();
if(subs !== ',') {
str = str+subs;
}
}
return str;
}