split string in two on given index and return both parts

Question

I have a string that I need to split on a given index and then return both parts, seperated by a comma. For example:

string: 8211 = 8,211
        98700 = 98,         


        

Answer 1

If code elegance ranks higher than the performance hit of regex, then

'1234567'.match(/^(.*)(.{3})/).slice(1).join(',')
=> "1234,567"

There's a lot of room to further modify the regex to be more precise.

If join() doesn't work then you might need to use map with a closure, at which point the other answers here may be less bytes and line noise.

Answer 2

You can also use number formatter JS available at

https://code.google.com/p/javascript-number-formatter/

Format options

http://jsfiddle.net/chauhangs/hUE3h/

  format("##,###.", 98700)
  format("#,###.", 8211)

Answer 3

ES6 1-liner

// :: splitAt = number => Array<any>|string => Array<Array<any>|string>
const splitAt = index => x => [x.slice(0, index), x.slice(index)]

console.log(
  splitAt(1)('foo'), // ["f", "oo"]
  splitAt(2)([1, 2, 3, 4]) // [[1, 2], [3, 4]]
)
  

Answer 4

You can also do it like this.
https://jsfiddle.net/Devashish2910/8hbosLj3/1/#&togetherjs=iugeGcColp

var str, result;
str = prompt("Enter Any Number");

var valueSplit = function (value, length) {
    if (length < 7) {
        var index = length - 3;
        return str.slice(0, index) + ',' + str.slice(index);
    }
    else if (length < 10 && length > 6) {
        var index1, index2;
        index1 = length - 6;
        index2 = length - 3;
        return str.slice(0,index1) + "," + str.slice(index1,index2) + "," + str.slice(index2);
    }
}

result = valueSplit(str, str.length);
alert(result);

Answer 5

Try this

function split_at_index(value, index)
{
 return value.substring(0, index) + "," + value.substring(index);
}

console.log(split_at_index('3123124', 2));

Answer 6

You can easily expand it to split on multiple indexes, and to take an array or string

const splitOn = (slicable, ...indices) =>
  [0, ...indices].map((n, i, m) => slicable.slice(n, m[i + 1]));

splitOn('foo', 1);
// ["f", "oo"]

splitOn([1, 2, 3, 4], 2);
// [[1, 2], [3, 4]]

splitOn('fooBAr', 1, 4);
//  ["f", "ooB", "Ar"]

lodash issue tracker: https://github.com/lodash/lodash/issues/3014