Develop Reference

I want my value modified to always have three decimal digits

My logic calculates and returns a value based on user input, I want to modify that value to always have three decimal digits
For example;
1 to 1.000
1.02 to 1.020
2.000004 to 2.000
2.5687 to 2.569
How would I achieve it on javascript?

You can use Number().toFixed() to do it
const formatVal = (val,precise = 3) =>{
return Number(val).toFixed(precise)
}
console.log(formatVal(1,3))
console.log(formatVal(1.02,3))
console.log(formatVal(2.000004,3))
console.log(formatVal(2.5687))
console.log("-----------------")
console.log(formatVal(2.5687,2))

You can do something like this,
let newNum = Number(1.34).toFixed(3);
console.log(newNum);

Javascript: how to get micronumbers in decimal format

I have simple function that calculates number of decimals,
eg. _d(0.01) = 2, _d(0.001) = 3 and so on.
We added some new coins to our system that have 0.00000001 quantity and function broke.
Here is why:
0.00000001.toString() = 1e-8, so I cant split it it by '.' and calculate length of second part as I did before.
So the question is - how to get string '0.00000001' out of 0.00000001 number easiest way.
EDIT
I didnt mean exactly '0.00000001', I meant any micronumber to decimal without exp. Some function _d(x) that would work _d(0.000000000012) = '0.000000000012'and so on. What usually toString() does to large (but not too large) numbers.

Use toFixed() with a large number of digits, then count the number of zeroes after the decimal point.
function _d(num) {
var str = num.toFixed(100);
var fraction = str.split('.')[1];
var zeros = fraction.match(/^0*/)[0].length;
return zeros + 1;
}
console.log(_d(0.1));
console.log(_d(0.01));
console.log(_d(0.000000001));

Do you want some thing like this
function decimalPlaces(num) {
var match = (''+num).match(/(?:\.(\d+))?(?:[eE]([+-]?\d+))?$/);
if (!match) { return 0; }
return Math.max(
0,
// Number of digits right of decimal point.
(match[1] ? match[1].length : 0)
// Adjust for scientific notation.
- (match[2] ? +match[2] : 0));
}
console.log(decimalPlaces(0.000000001))

First off, I got some inspiration for this answer from here:
How to avoid scientific notation for large numbers in JavaScript?
You can convert the number to a strong and then check for str.indexOf("e"). If true, then just return the scientific notation part of the string. For example:
function _d() {
// your current function here
if (str.indexOf("e")) {
var something = str.split("-")[1];
return something;
}
}
EDIT: I was working on this before your last comment to me, so this returns a string of the number, which I thought was what you wanted.
Leaving aside the point about significant digits, which is meaningful and correct but does not solve your problem, try this. We take the number, convert to string, if that string is not scientific notation then the answer is trivial. If it is scientific notation, then split the string twice (once on "e-" and then split the zeroth array on "." Add str[1]-1 zeroes to the lead of the number and add the digits to the end.
function _d(arg) {
var str = arg.toString();
if (str.indexOf("e-")) {
var digits = str.split("e-")[0];
var zeroes = str.split("e-")[1];
var zero = Number(zeroes);
var each = digits.split(".");
var something = "0.";
for (var i = 0; i < zeroes-1; i++) {
something += "0";
}
for (var j = 0; j < each.length; j++) {
something = something + each[j];
}
return something;
}
}
This won't work with very large numbers or very small negative numbers. And its pretty convoluted.

The other way is to use .toString() and then look for .length-2(2 characters - '0.'. It should give you the number of zeros.
The advantage of this method is you don't need to know the number of maximum decimals in the number.

To keep it as the full decimal:
Number(0.000001)
// 0.000001
To show it as a string:
0.000001.toFixed(6)
// "0.000001"

Converting number string to comma version

I have a Angular 2 / Typescript application string that contains number representations such as the following...
10000
10000.50
-10000
-10000.50
0
I want to add in commas after the thousand mark, for example...
10,000
10,000.50
-10,000
-10,000.50
0
What is the best way to do this?
I have tried some other answers but nothing is quite right.
For example this.value.toString().replace(/(\d)(?=(\d{3})+(?!\d))/g, "$1,"); and this.value.toLocaleString(); don't seem to handle both the comman and decimal point.

Have you tried
var some_string_value = '-10000.50';
parseFloat(some_string_value).toLocaleString()
?

Use "indexOf('.')",splice to two part,then use the method you found.
function addComma(num){
//some type check here
var numStr = num.toString();
var intEnd = numStr.indexOf('.');
var onePart =numStr,otherPart ='';
if(intEnd !== -1){
var onePart = numStr.slice(0,intEnd);
var otherPart = numStr.slice(intEnd);
}
return onePart.replace(/(\d)(?=(?:\d{3})+$)/g, '$1,')+otherPart;
}

You can use a pipe, you can find a full answer to your question here: Add Comma Separated Thousands to Number Inputs in Angular2

Rounding up to two decimal place in javascript eg 4.9995 to 4.99 in mathematical way in js

How can I convert decimal number to 2 decimal place number?
Example: I want to connvert 4.995 to 4.99 but javascript is returning 5.00.
var price=4.995;
var rounded_price=price.toFixed(2);
console.log(rounded_price);

I wouldn't call it rounding but you can achieve it by:
function trim2Dec(n) {
return Math.floor(n * 100) / 100;
}
alert(trim2Dec(4.995));

You can use regex for this as the following:
alert("4.995".replace(/(\d+(\.\d{1,2})?)\d*/, "$1"))

This is Pretty simple check out this code
var price=4.995;
var price1=4.985;
var rounded_price=(Math.round(price*100)/100);
var rounded_price1=(Math.round(price1*100)/100);
console.log("price : "+rounded_price+" price1 : "+rounded_price1);
here at first i am multiplying the price and then i have divided it with 100..just as we do to find the percentage of any number.

JavaScript displaying a float to 2 decimal places

I wanted to display a number to 2 decimal places.
I thought I could use toPrecision(2) in JavaScript .
However, if the number is 0.05, I get 0.0500. I'd rather it stay the same.
See it on JSbin.
What is the best way to do this?
I can think of coding a few solutions, but I'd imagine (I hope) something like this is built in?

float_num.toFixed(2);
Note:toFixed() will round or pad with zeros if necessary to meet the specified length.

You could do it with the toFixed function, but it's buggy in IE. If you want a reliable solution, look at my answer here.

number.parseFloat(2) works but it returns a string.
If you'd like to preserve it as a number type you can use:
Math.round(number * 100) / 100

Don't know how I got to this question, but even if it's many years since this has been asked, I would like to add a quick and simple method I follow and it has never let me down:
var num = response_from_a_function_or_something();
var fixedNum = parseFloat(num).toFixed( 2 );

with toFixed you can set length of decimal points like this:
let number = 6.1234
number.toFixed(2) // '6.12'
but toFixed returns a string and also if number doesn't have decimal point at all it will add redundant zeros.
let number = 6
number.toFixed(2) // '6.00'
to avoid this you have to convert the result to a number. you can do this with these two methods:
let number1 = 6
let number2 = 6.1234
// method 1
parseFloat(number1.toFixed(2)) // 6
parseFloat(number2.toFixed(2)) // 6.12
// method 2
+number1.toFixed(2) // 6
+number2.toFixed(2) // 6.12

Try toFixed instead of toPrecision.

function round(value, decimals) {
return Number(Math.round(value+'e'+decimals)+'e-'+decimals);
}
round(1.005, 2); // return 1.01
round(1.004, 2); // return 1 instead of 1.00
The answer is following this link: http://www.jacklmoore.com/notes/rounding-in-javascript/

I used this way if you need 2 digits and not string type.
const exFloat = 3.14159265359;
console.log(parseFloat(exFloat.toFixed(2)));

You could try mixing Number() and toFixed().
Have your target number converted to a nice string with X digits then convert the formated string to a number.
Number( (myVar).toFixed(2) )
See example below:
var myNumber = 5.01;
var multiplier = 5;
$('#actionButton').on('click', function() {
$('#message').text( myNumber * multiplier );
});
$('#actionButton2').on('click', function() {
$('#message').text( Number( (myNumber * multiplier).toFixed(2) ) );
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
<button id="actionButton">Weird numbers</button>
<button id="actionButton2">Nice numbers</button>
<div id="message"></div>

The toFixed() method formats a number using fixed-point notation.
and here is the syntax
numObj.toFixed([digits])
digits argument is optional and by default is 0. And the return type is string not number. But you can convert it to number using
numObj.toFixed([digits]) * 1
It also can throws exceptions like TypeError, RangeError
Here is the full detail and compatibility in the browser.

let a = 0.0500
a.toFixed(2);
//output
0.05

There's also the Intl API to format decimals according to your locale value. This is important specially if the decimal separator isn't a dot "." but a comma "," instead, like it is the case in Germany.
Intl.NumberFormat('de-DE').formatToParts(0.05).reduce((acc, {value}) => acc += value, '');
Note that this will round to a maximum of 3 decimal places, just like the round() function suggested above in the default case. If you want to customize that behavior to specify the number of decimal places, there're options for minimum and maximum fraction digits:
Intl.NumberFormat('de-DE', {minimumFractionDigits: 3}).formatToParts(0.05)

float_num = parseFloat(float_num.toFixed(2))

I have made this function. It works fine but returns string.
function show_float_val(val,upto = 2){
var val = parseFloat(val);
return val.toFixed(upto);
}