convert digital display format

quick question, I have some integrate variable in javascript, say: 123456, or 123456789, it can be any valid number. Now, I would like to convert the number to a string like "123,456" or "123,456,789". Does anyone have a good algorithm for this? Of course, it should work for any numbers. For example: for 2000 ---> 2,000; 123456--->开发者_开发百科123,456

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Give this a shot.

var num = 12345678;
var str = num + "";  // cast to string
var out = [];
for (var i = str.length - 3; i > 0; i -= 3) {
    out.unshift(str.substr(i, 3));
}
out.unshift(str.substr(0, 3 + i));
out = out.join(',');  // "12,345,678"

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in addition to the other excellent solution

var n = 999999
var s = n.toLocaleString()