Print number in comma-splited format in JavaScript.

commaSplitNumber.js

// Print number in comma-splited format.
// Written by physacco. 2011-05-13.
//
// Tested on:
// - Mozilla SpiderMonkey JavaScript-C 1.7.0 2007-10-03.
// - Mozilla Rhino 1.7 release 0.7.r2.fc12 2009 07 28.

function commaSplitNumber(num) {
    var numstr = num.toString();
    var dec, frac;
    var tmp = numstr.split(".");
    dec = tmp[0];
    frac = tmp[1];

    var dec_len = dec.length;
    var loop_rem = dec_len % 3;
    var loop_max = (dec_len - loop_rem) / 3;

    var segs = [];
    for(var i = 0; i < loop_max; i++) {
        var end = dec_len - i * 3;
        var beg = end - 3;
        var sub = numstr.substring(beg, end);
        segs.unshift(sub);
    }
    if(loop_rem) {
        segs.unshift(numstr.substring(0, loop_rem));
    }

    var ret = segs.join(",");
    if(frac) {
        ret += "." + frac;
    }
    return ret;
}

// To run it with nodejs, substitute print with console.log.
print(commaSplitNumber("123456"));
print(commaSplitNumber("12345678"));
print(commaSplitNumber("12345678.12345"));

// Output:
// 123,456
// 12,345,678
// 12,345,678.12345