wait until a function finishes javascript

1function firstFunction(_callback){
2    // do some asynchronous work
3    // and when the asynchronous stuff is complete
4    _callback();    
5}
6
7function secondFunction(){
8    // call first function and pass in a callback function which
9    // first function runs when it has completed
10    firstFunction(function() {
11        console.log('huzzah, I\'m done!');
12    });    
13}