Optimizing (and Debugging) Javascript With Firebug

firebug-console-execution-time.js

console.time();
var str = '';
for (var i = 0; i < 1000; i++) {
    str += i;
}
console.timeEnd();

firebug-console-profiler.js

console.profile();
for (var i = 0; i < 1000; i++) {
    testFunction();
}
console.profileEnd();

function testFunction() {
    // dummy function
}

firebug-console-stack-trace.js

console.trace();