JavaScript Random String Value

random_value.js

function randomString() {
    var chars = "0123456789";
    var string_length = 7;
    var randomstring = '';
    for (var i = 0; i < string_length; i++) {
        var rnum = Math.floor(Math.random() * chars.length);
        randomstring += chars.substring(rnum, rnum + 1);
    }
    return randomstring;
}