console.time.js

var c = {
    hash: {},
    useNative: true,
    time: function(str){
        if (this.useNative && console && console.time) console.time(str);
        else this.hash[str] = (new Date()).getTime();
    },
    timeEnd: function(str){
        if (this.useNative && console && console.time && console.timeEnd) console.timeEnd(str);
        else if (this.hash[str]){
            this.log( str + ': ' + ((new Date()).getTime() - this.hash[str]) + 'ms' );
            this.hash[str] = undefined;
        }
    },
    log: function(str){
        console && console.log && console.log.apply(console, arguments);
    }
};

// usage:

c.time('my test case');
// do work here
c.timeEnd('my test case');

//prints:
//> my test case: XXXms