Adding extra zeros in front of a number using jQuery?

Question

I have file that are uploaded which are formatted like so

MR 1

MR 2

MR 100

MR 200

MR 300

Answer 1

Just for a laugh do it the long nasty way....:
(NOTE: ive not used this, and i would not advise using this.!)

function pad(str, new_length) {
    ('00000000000000000000000000000000000000000000000000' + str).
    substr((50 + str.toString().length) - new_length, new_length)
}