在另一个匿名函数中嵌入一个匿名函数

Question

I have a hash called options. The problem that I'm facing is that options['beforeOpen'] might already be a function, in which case I don't want to overwrite it. I'd like to instead call it then call another function that needs to be called every time

In this example the method that needs to be called every time is methodThatINeedToDo . I thought the code below would accomplish this but it's not working as I expected.

function methodThatINeedToDo(){alert('maintenance');}

var options = {beforeOpen: function(){alert('first');}} 
if(typeof options['beforeOpen'] == "function"){
    options['beforeOpen'] = function(){options['beforeOpen'].call(); methodThatINeedToAddToDo();}
} else {
    options['beforeOpen'] = methodThatINeedToDo;
}

Answer 1

The problem is that within the function you're defining to override options['beforeOpen'] , you're using options['beforeOpen'] , which by that time has been overwritten!

You need to cache it and use the cached value within your new function:

var cachedBeforeOpen = options.beforeOpen;

if (typeof cachedBeforeOpen == "function") {
  options.beforeOpen = function() {
    cachedBeforeOpen.call();
    methodThatINeedToDo();
  };
} else {
  options.beforeOpen = methodThatINeedToDo;
}

Answer 2

Simply always call methodThatINeedToDo , since you want to and in there check to see if you should call your options method:

function methodThatINeedToDo(){
  options.beforeOpen && options.beforeOpen();
  alert('maintenance');
}

Answer 3

That really smells like the wrong solution. Why not Publish/Subscribe pattern ?

Here's a little example: http://jsfiddle.net/ajyQH/

$(function() {

var yourObj = { yourFct : [] };


$('#btn').click(function() {
    yourObj.yourFct.push(function() {
        $('#testibert').append($('<p>').text('hallo'));
    });
});

$('#btn_exec').click(function() {
    var len = yourObj.yourFct.length;
    for(var i = 0; i < len; i++) {
      yourObj.yourFct[i]();
    }
});
});

Answer 4

var oldCall = options['beforeOpen'];
var newCall = function(){
 oldCall(); 
 methodThatINeedToAddToDo();
};
options['beforeOpen'] = newCall;