Useful console.log patch for Chrome showing how much time have been passed since last time console.log was run.

console.timelog.js

/*

console.log output example:

=====================================================================================
Date                            Total      Diff       Message
=====================================================================================
Wed Jan 30 2013 3:3:47:376      0ms         0ms       start
Wed Jan 30 2013 3:3:47:382      6ms        +6ms       started hotels loading
Wed Jan 30 2013 3:3:47:502      126ms      +120ms     loaded: /optimizely/main.js (1)
Wed Jan 30 2013 3:3:47:723      347ms      +221ms     DOM content loaded

*/

console.log = function (){

    function repeatChar(char, count){
        return new Array(count + 1).join(char);
    };

    function humanizeTime(timestamp){
        var humanized = [];
        var date = new Date(timestamp);
        var data = {
            h: date.getUTCHours(),
            m: date.getUTCMinutes(),
            s: date.getUTCSeconds(),
            ms: date.getUTCMilliseconds()
        };

        for ( var prop in data ) {
            if ( data[prop] || !true ) {
                humanized.push(data[prop] + prop);
            }
        }
        if ( !humanized.length ) {
            humanized.push('0ms');
        }
        return humanized.join(' ');
    };

    const dateColumnLength = 37;
    const totalTimeColumnLength = 18;
    const prevTimeColumnLength = 15;

    var currentTime = new Date();
    var diffStart = console._startTime ? +currentTime - +console._startTime : 0;
    var diffPrevious = console._previousTime ? +currentTime - +console._previousTime : 0;

    var value = [
        currentTime.toDateString(), ' ',
        currentTime.getHours(), ':',
        currentTime.getMinutes(), ':',
        currentTime.getSeconds(), ':',
        currentTime.getMilliseconds()
    ].join('');

    value += repeatChar(' ', dateColumnLength - value.length);
    value += humanizeTime(diffStart);
    value += repeatChar(' ', dateColumnLength + totalTimeColumnLength - value.length);
    value += ( diffPrevious ? '+' : ' ' ) + diffPrevious + 'ms';
    value += repeatChar(' ', dateColumnLength + totalTimeColumnLength + prevTimeColumnLength - value.length);

    Array.prototype.unshift.call(arguments, value);
    if ( !console._startTime ) {
        console._startTime = currentTime;
    }
    console._previousTime = currentTime;
    console.constructor.prototype.log.apply(console, arguments);
};