Format numbers in JavaScript similar to C#

Question

Is there a simple way to format numbers in JavaScript, similar to the formatting methods available in C# (or VB.NET) via ToString(\"format_provider\") or

Answer 1

Here's a simple JS function to add commas to an integer number in string format. It will handle whole numbers or decimal numbers. You can pass it either a number or a string. It obviously returns a string.

function addCommas(str) {
    var parts = (str + "").split("."),
        main = parts[0],
        len = main.length,
        output = "",
        first = main.charAt(0),
        i;

    if (first === '-') {
        main = main.slice(1);
        len = main.length;    
    } else {
        first = "";
    }
    i = len - 1;
    while(i >= 0) {
        output = main.charAt(i) + output;
        if ((len - i) % 3 === 0 && i > 0) {
            output = "," + output;
        }
        --i;
    }
    // put sign back
    output = first + output;
    // put decimal part back
    if (parts.length > 1) {
        output += "." + parts[1];
    }
    return output;
}

Here's a set of test cases: http://jsfiddle.net/jfriend00/6y57j/

You can see it being used in this previous jsFiddle: http://jsfiddle.net/jfriend00/sMnjT/. You can find functions that will handle decimal numbers too with a simple Google search for "javascript add commas".

Converting a number to a string can be done many ways. The easiest is just to add it to a string:

var myNumber = 3;
var myStr = "" + myNumber;   // "3"

Within, the context of your jsFiddle, you'd get commas into the counter by changing this line:

jTarget.text(current);

to this:

jTarget.text(addCommas(current));

You can see it working here: http://jsfiddle.net/jfriend00/CbjSX/