Adding commas to numbers when typing

Question

I am trying to add commas when the user type a number. What is the correct syntax to select the input form-control class with attribute number type in Jquery?

EDIT: I can't change the HTML code since it is outputted from Django with Bootstrap.

HTML

<span class="input-group-addon">$</span>
<input class="form-control" id="id_step2-number_2"
       name="step2-number_2" type="number">
<span class="input-group-addon">.00</span>

JQuery

$(document).ready(function(){
    $("input[type='number']").keyup(function(event){
        // skip for arrow keys
        if(event.which >= 37 && event.which <= 40){
            event.preventDefault();
        }
        var $this = $(this);
        var num = $this.val().replace(/,/gi, "")
            .split("").reverse().join("");
          
        var num2 = RemoveRougeChar(
            num.replace(/(.{3})/g,"$1,").split("")
                .reverse().join("")
        );
          
        console.log(num2);

        // the following line has been simplified.
        // Revision history contains original.
        $this.val(num2);
    });
});
    
function RemoveRougeChar(convertString){
    if(convertString.substring(0,1) == ","){
        return convertString.substring(1, convertString.length)            
    }
    return convertString;
}

JSFiddle Link https://jsfiddle.net/yWTLk/767/

Answer 1

Using the input type "number" seems to prevent inserting commas into the input field with Javascript. If you'd like to insert commas, you may want to use a "text" input instead, but this will prevent numeric validation on browsers with Javascript disabled.

The fun will never end, it's HTML5.

Answer 2

First of all, you can't use input type=number, because it won't allow the character , which you are using to notate number group.

Second, with a good regular expression, this is actually super easy, and really no need for reverse and reverse, which is boring.

var num = $this.val().replace(/,/gi, "");
var num2 = num.split(/(?=(?:\d{3})+$)/).join(",");

The first line removes commas from input value.
The second line is magic, it splits the value into groups of 3 from last to first, then join with comma. For example, '1234567' will become ['1', '234', '567'].

I use split here is just to show the power of RegExp, in practice we don't need to split and join, just replace directly:

var num2 = num.replace(/\d(?=(?:\d{3})+$)/g, '$&,');

fiddle

But, the real magic is, I bet you would yell, toLocaleString! What?!

(1234567).toLocaleString() // "1,234,567"