Create a unique number with javascript time

Question

I need to generate unique id numbers on the fly using javascript. In the past, I\'ve done this by creating a number using time. The number would be made up of the four digi

Answer 1

This performs faster than creating a Date instance, uses less code and will always produce a unique number (locally):

function uniqueNumber() {
    var date = Date.now();

    // If created at same millisecond as previous
    if (date <= uniqueNumber.previous) {
        date = ++uniqueNumber.previous;
    } else {
        uniqueNumber.previous = date;
    }

    return date;
}

uniqueNumber.previous = 0;

jsfiddle: http://jsfiddle.net/j8aLocan/

I've released this on Bower and npm: https://github.com/stevenvachon/unique-number

You could also use something more elaborate such as cuid, puid or shortid to generate a non-number.