Question

I’m using this prototype to format strings in javascript:

String.prototype.format = function () {
            var args = arguments;

            return this.replace(/{(\d+)}/g, function (match, number) {
                return typeof args[number] != 'undefined'
                    ? args[number]
                    : match
                    ;
            });
        };

While it works fine, It doesn’t do all I would like to do. If I have a string that is supposed to be formatted as {0:000000}, this will not fix it.
How can I extend this, to add the extra 0’s to my string?
I can easily detect them, by fixing the regexp, but how do I format the return correctly?

Answer 1

Calling toFixed( ) on a float will round/pad it accordingly if that helps?

So you can check for a float in the same way you check it’s not undefined. If you’ve got one, you do args[number].toFixed(6).

You could also build in additional flexibility by extending your regex to parse your template to function similarly to python (e.g. ‘{.3f}’ for 3 d.p)