Solution 1:

For integers use

function numberWithSpaces(x) {
    return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, " ");
}

For floating point numbers you can use

function numberWithSpaces(x) {
    var parts = x.toString().split(".");
    parts[0] = parts[0].replace(/\B(?=(\d{3})+(?!\d))/g, " ");
    return parts.join(".");
}

This is a simple regex work. https://developer.mozilla.org/en-US/docs/JavaScript/Guide/Regular_Expressions << Find more about Regex here.

If you are not sure about whether the number would be integer or float, just use 2nd one...

Solution 2:

Easiest way:

1

var num = 1234567890,
result = num.toLocaleString() ;// result will equal to "1 234 567 890"

2

var num = 1234567.890,
result = num.toLocaleString() + num.toString().slice(num.toString().indexOf('.')) // will equal to 1 234 567.890

3

var num = 1234567.890123,
result = Number(num.toFixed(0)).toLocaleString() + '.' + Number(num.toString().slice(num.toString().indexOf('.')+1)).toLocaleString()
//will equal to 1 234 567.890 123

4

If you want ',' instead of ' ':

var num = 1234567.890123,
result = Number(num.toFixed(0)).toLocaleString().split(/\s/).join(',') + '.' + Number(num.toString().slice(num.toString().indexOf('.')+1)).toLocaleString()
//will equal to 1,234,567.890 123

If not working, set the parameter like: "toLocaleString('ru-RU')" parameter "en-EN", will split number by the ',' instead of ' '