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How to format numbers in javascript to two decimal digits?

I need to format numbers to two decimal digits in javascript. In order to do this I am using toFixed method which is working properly.
But in cases, where numbers don't have any decimal digits, it should not show decimal point
e.g. 10.00 should be 10 only and not 10.00.

.toFixed() converts the result to String,
so you need to convert it back to Number:
parseFloat( num.toFixed(2) )
or by simply using the Unary +
+num.toFixed(2)
both will give the following:
// 15.00 ---> 15
// 15.20 ---> 15.2
If you only want to get rid of the .00 case, than you can go for String manipulation using .replace()
num.toFixed(2).replace('.00', '');
Note: the above will convert your Number to String.

As an alternative to make this change global(if you need, of course), try this:
var num1 = 10.1;
var num2 = 10;
var tofixed = Number.prototype.toFixed;
Number.prototype.toFixed = function(precision)
{
var num = this.valueOf();
if (num % 1 === 0)
{
num = Number(num + ".0");
}
return tofixed.call(num, precision);
}
console.log(num1.toFixed(2));
console.log(num2.toFixed(2));
Fiddle. This is a mix of this and this post.

using the digits of a number as an array

var number = 342345820139586830203845861938475676
var output = []
var sum = 0;
while (number) {
output.push(number % 10);
number = Math.floor(number/10);
}
output = output.reverse();
function addTerms () {
for (i = 0; i < output.length; i=i+2) {
var term = Math.pow(output[i], output[i+1]);
sum += term;
}
return sum;
}
document.write(output);
document.write("<br>");
document.write(addTerms());
I am trying to take that large number and split it into its digits. Then, find the sum of the the first digit raised to the power of the 2nd, 3rd digit raiseed to the 4th, 5th raised to the 6th and so on. for some reason, my array is returning weird digits, causing my sum to be off. the correct answer is 2517052. Thanks

You're running into precision issues within JavaScript. Just evaluate the current value of number before you start doing anything, and the results may surprise you:
>>> var number = 342345820139586830203845861938475676; number;
3.423458201395868e+35
See also: What is JavaScript's highest integer value that a Number can go to without losing precision?
To resolve your issue, I'd store your input number as an array (or maybe even a string), then pull the digits off of that.
This will solve your calculation with the expected result of 2517052:
var number = "342345820139586830203845861938475676";
var sum = 0;
for(var i=0; i<number.length; i=i+2){
sum += Math.pow(number.charAt(i), number.charAt(i+1));
}
sum;

JavaScript stores numbers in floating point format (commonly double). double can store precisely only 15 digits.
You can use string to store this large number.

As mentioned, this is a problem with numeric precision. It applies to all programming languages that use native numeric formats. Your problem works fine if you use a string instead
var number = '342345820139586830203845861938475676'
var digits = number.split('')
var total = 0
while (digits.length > 1) {
var [n, power] = digits.splice(0, 2)
total += Math.pow(n, power)
}
(the result is 2517052, byt the way!)

Cast the number as a string and then iterate through it doing your math.
var number = "342345820139586830203845861938475676";//number definition
var X = 0;//some iterator
var numberAtX = 0 + number.charAt(X);//number access

The greatest integer supported by Javascript is 9007199254740992. So that only your output is weird.
For Reference go through the link http://ecma262-5.com/ELS5_HTML.htm#Section_8.5

[edit] adjusted the answer based on Borodins comment.
Mmm, I think the result should be 2517052. I'd say this does the same:
var numbers = '342345820139586830203845861938475676'.split('')
,num = numbers.splice(0,2)
,result = Math.pow(num[0],num[1]);
while ( (num = numbers.splice(0,2)) && num.length ){
result += Math.pow(num[0],num[1]);
}
console.log(result); //=> 2517052

The array methods map and reduce are supported in modern browsers,
and could be worth defining in older browsers. This is a good opportunity,
if you haven't used them before.
If you are going to make an array of a string anyway,
match pairs of digits instead of splitting to single digits.
This example takes numbers or strings.
function sumPower(s){
return String(s).match(/\d{2}/g).map(function(itm){
return Math.pow(itm.charAt(0), itm.charAt(1));
}).reduce(function(a, b){
return a+b;
});
}
sumPower('342345820139586830203845861938475676');
alert(sumPower(s))
/*
returned value:(Number)
2517052
*/

Round the value in Javascript

I have scenario where if user enters for example 000.03, I want to show the user it as .03 instead of 000.03. How can I do this with Javascript?

You can use a regular expression:
"000.03".replace(/^0+\./, ".");
Adjust it to your liking.

This actually is trickier than it first seems. Removing leading zero's is not something that is standard Javascript. I found this elegant solution online and edited it a bit.
function removeLeadingZeros(strNumber)
{
while (strNumber.substr(0,1) == '0' && strNumber.length>1)
{
strNumber = strNumber.substr(1);
}
return strNumber;
}
userInput = "000.03";
alert(removeLeadingZeros(userInput));

How about:
function showRounded(val) {
var zero = parseInt(val.split('.')[0],10) === 0;
return zero ? val.substring(val.indexOf('.')) : val.replace(/^0+/,'') );
}
console.log(showRounded('000.03')); //=> ".03"
console.log(showRounded('900.03')); //=> "900.03"
console.log(showRounded('009.03')); //=> "9.03"
Or adjust Álvaro G. Vicario's solution to get rid of leading zero's into:
String(parseFloat("090.03")).replace(/^0+\./, ".")

This function will take any string and try to parse it as a number, then format it the way you described:
function makePretty(userInput) {
var num,
str;
num = parseFloat(userInput); // e.g. 0.03
str = userInput.toString();
if (!isNaN(num) && str.substring(0, 1) === '0') {
str = str.substring(1); // e.g. .03
} else if (isNaN(num)) {
str = userInput; // it’s not a number, so just return the input
}
return str;
}
makePretty('000.03'); // '.03'
makePretty('020.03'); // '20.03'
It you feed it something it cannot parse as a number, it will just return it back.
Update: Oh, I see If the single leading zero needs to be removed as well. Updated the code.

Assuming your input's all the same format, and you want to display the .
user = "000.03";
user = user.substring(3);

You can convert a string into a number and back into a string to format it as "0.03":
var input = "000.03";
var output = (+input).toString(); // "0.03"
To get rid of any leading zeroes (e.g. ".03"), you can do:
var input = "000.03";
var output = input.substr(input.indexOf(".")); // ".03"
However, this improperly strips "20.30" to ".30". You can combine the first two methods to get around this:
var input = "000.03";
var output = Math.abs(+input) < 1 ?
input.substr(input.indexOf(".")) :
(+"000.03").toString();

How do I select the nth digit in a large integer inside javascript?

When I want to select the nth character, I use the charAt() method, but what's the equivalent I can use when dealing with integers instead of string values?

Use String():
var number = 132943154134;
// convert number to a string, then extract the first digit
var one = String(number).charAt(0);
// convert the first digit back to an integer
var one_as_number = Number(one);

It's a stupid solution but seems to work without converting to string.
var number = 123456789;
var pos = 4;
var digit = ~~(number/Math.pow(10,pos))- ~~(number/Math.pow(10,pos+1))*10;

You could convert the number to a string and do the same thing:
parseInt((number + '').charAt(0))

If you want an existing method, convert it to a string and use charAt.
If you want a method that avoids converting it to a string, you could play games with dividing it by 10 repeatedly to strip off enough digits from the right -- say for 123456789, if you want the 3rd-from-right digit (6), divide by 10 3 times yielding 123456, then take the result mod 10 yielding 6. If you want to start counting digits from the left, which you probably do, then you need to know how many digits (base 10) are in the entire number, which you could deduce from the log base 10 of the number... All this is unlikely to be any more efficient than just converting it to a string.

function digitAt(val, index) {
return Math.floor(
(
val / Math.pow(10, Math.floor(Math.log(Math.abs(val)) / Math.LN10)-index)
)
% 10
);
};
digitAt(123456789, 0) // => 1
digitAt(123456789, 3) // => 4
A bit messy.
Math.floor(Math.log(Math.abs(val)) / Math.LN10)
Calculates the number of digits (-1) in the number.

var num = 123456;
var secondChar = num.toString()[1]; //get the second character

var number = 123456789
function return_digit(n){
r = number.toString().split('')[n-1]*1;
return r;
}
return_digit(3); /* returns 3 */
return_digit(6); /* returns 6 */

How to parse float with two decimal places in javascript?

I have the following code. I would like to have it such that if price_result equals an integer, let's say 10, then I would like to add two decimal places. So 10 would be 10.00.
Or if it equals 10.6 would be 10.60. Not sure how to do this.
price_result = parseFloat(test_var.split('$')[1].slice(0,-1));

You can use toFixed() to do that
var twoPlacedFloat = parseFloat(yourString).toFixed(2)

If you need performance (like in games):
Math.round(number * 100) / 100
It's about 100 times as fast as parseFloat(number.toFixed(2))
http://jsperf.com/parsefloat-tofixed-vs-math-round

When you use toFixed, it always returns the value as a string. This sometimes complicates the code. To avoid that, you can make an alternative method for Number.
Number.prototype.round = function(p) {
p = p || 10;
return parseFloat( this.toFixed(p) );
};
and use:
var n = 22 / 7; // 3.142857142857143
n.round(3); // 3.143
or simply:
(22/7).round(3); // 3.143

To return a number, add another layer of parentheses. Keeps it clean.
var twoPlacedFloat = parseFloat((10.02745).toFixed(2));

If your objective is to parse, and your input might be a literal, then you'd expect a float and toFixed won't provide that, so here are two simple functions to provide this:
function parseFloat2Decimals(value) {
return parseFloat(parseFloat(value).toFixed(2));
}
function parseFloat2Decimals(value,decimalPlaces) {
return parseFloat(parseFloat(value).toFixed(decimalPlaces));
}

ceil from lodash is probably the best
_.ceil("315.9250488",2)
_.ceil(315.9250488,2)
_.ceil(undefined,2)
_.ceil(null,2)
_.ceil("",2)
will work also with a number and it's safe

You can use .toFixed() to for float value 2 digits
Exampale
let newValue = parseFloat(9.990000).toFixed(2)
//output
9.99

I have tried this for my case and it'll work fine.
var multiplied_value = parseFloat(given_quantity*given_price).toFixed(3);
Sample output:
9.007

parseFloat(parseFloat(amount).toFixed(2))
You have to parse it twice. The first time is to convert the string to a float, then fix it to two decimals (but the toFixed returns a string), and finally parse it again.

Please use below function if you don't want to round off.
function ConvertToDecimal(num) {
num = num.toString(); //If it's not already a String
num = num.slice(0, (num.indexOf(".")) + 3); //With 3 exposing the hundredths place
alert('M : ' + Number(num)); //If you need it back as a Number
}

For what its worth: A decimal number, is a decimal number, you either round it to some other value or not. Internally, it will approximate a decimal fraction according to the rule of floating point arthmetic and handling. It stays a decimal number (floating point, in JS a double) internally, no matter how you many digits you want to display it with.
To present it for display, you can choose the precision of the display to whatever you want by string conversion. Presentation is a display issue, not a storage thing.

#sd
Short Answer: There is no way in JS to have Number datatype value with trailing zeros after a decimal.
Long Answer: Its the property of toFixed or toPrecision function of JavaScript, to return the String. The reason for this is that the Number datatype cannot have value like a = 2.00, it will always remove the trailing zeros after the decimal, This is the inbuilt property of Number Datatype. So to achieve the above in JS we have 2 options
Either use data as a string or
Agree to have truncated value with case '0' at the end ex 2.50 -> 2.5.

You can store your price as a string
You can use
Number(string)
for your calculations.
example
Number("34.50") == 34.5
also
Number("35.65") == 35.65
If you're comfortable with the Number function , you can go with it.

Try this (see comments in code):
function fixInteger(el) {
// this is element's value selector, you should use your own
value = $(el).val();
if (value == '') {
value = 0;
}
newValue = parseInt(value);
// if new value is Nan (when input is a string with no integers in it)
if (isNaN(newValue)) {
value = 0;
newValue = parseInt(value);
}
// apply new value to element
$(el).val(newValue);
}
function fixPrice(el) {
// this is element's value selector, you should use your own
value = $(el).val();
if (value == '') {
value = 0;
}
newValue = parseFloat(value.replace(',', '.')).toFixed(2);
// if new value is Nan (when input is a string with no integers in it)
if (isNaN(newValue)) {
value = 0;
newValue = parseFloat(value).toFixed(2);
}
// apply new value to element
$(el).val(newValue);
}

Solution for FormArray controllers
Initialize FormArray form Builder
formInitilize() {
this.Form = this._formBuilder.group({
formArray: this._formBuilder.array([this.createForm()])
});
}
Create Form
createForm() {
return (this.Form = this._formBuilder.group({
convertodecimal: ['']
}));
}
Set Form Values into Form Controller
setFormvalues() {
this.Form.setControl('formArray', this._formBuilder.array([]));
const control = <FormArray>this.resourceBalanceForm.controls['formArray'];
this.ListArrayValues.forEach((x) => {
control.push(this.buildForm(x));
});
}
private buildForm(x): FormGroup {
const bindvalues= this._formBuilder.group({
convertodecimal: x.ArrayCollection1? parseFloat(x.ArrayCollection1[0].name).toFixed(2) : '' // Option for array collection
// convertodecimal: x.number.toFixed(2) --- option for two decimal value
});
return bindvalues;
}

I've got other solution.
You can use round() to do that instead toFixed()
var twoPlacedFloat = parseFloat(yourString).round(2)

The solution that work for me is the following
parseFloat(value)