javascript file size format human readable

filesizeformat.js

function filesizeformat(bytes, binary, precision) {
    /*
        Javascript filesizeformater.
        Inspired by jinja2 and some gists.

        @version 1.0.0
        @copyright 2014 Julian Hille
        @author Julian Hille
     */
    binary = typeof binary !== 'undefined' ? binary : false;
    precision = typeof precision !== 'undefined' ? precision : 2;
    var base = binary ? 1024 : 1000;
    var prefixes = [
        (binary ? 'KiB' : 'kB'),
        (binary ? 'MiB' : 'MB'),
        (binary ? 'GiB' : 'GB'),
        (binary ? 'TiB' : 'TB'),
        (binary ? 'PiB' : 'PB'),
        (binary ? 'EiB' : 'EB'),
        (binary ? 'ZiB' : 'ZB'),
        (binary ? 'YiB' : 'YB')
    ]
    if (!isFinite(bytes)) {
      return '- Bytes';
    }
    else if (bytes == 1) {
        return '1 Byte';
    }
    else if (bytes < base) {
        return bytes + ' Bytes';
    }
    var index = Math.floor(Math.log(bytes) / Math.log(base));
    return parseFloat((bytes / Math.pow(base, Math.floor(index))).toFixed(precision)).toString() +  ' ' + prefixes[index-1];
}