Question

The jQuery documentation for both basically states the same thing so I was wondering if there’s any major difference, if any, between the two. Thanks!

Answer 1

The documentation on this is actually really bad, so here’s what I found by studying the source code:

lock only prevents future fire calls, but does not prevent functions to be added.

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Here’s a quick rundown of the methods:

• empty – Removes any callbacks registered thus far.
• lock – Prevents further calls to fire, but allows more callbacks to be added.
• disable – Prevents further calls to both fire & add.

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To understand all this, let’s start with an explanation of the memory flag:

If the callback object is constructed with the memory flag, it’ll keep track of the last fire call, and any callback added later will immediately be called. Here’s an example:

var callbacks = $.Callbacks('memory');

callbacks.add(function(){
    console.log('first');
});

callbacks.fire();

callbacks.add(function(){
    console.log('second');
});

This’ll also log second, even though it was added after the fire call.

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If you disable it though, it’ll completely wipe the memory. Here’s another example:

var callbacks = $.Callbacks('memory');

callbacks.add(function(){
    console.log('first');
});

callbacks.fire();
callbacks.disable();

callbacks.add(function(){
    console.log('second');
});

callbacks.fire();

This’ll only log first, since callbacks has been disabled before the second function was added.

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However, if you use lock it instead, functions added later will be called. Here’s another example:

var callbacks = $.Callbacks('memory');

callbacks.add(function(){
    console.log('first');
});

callbacks.fire();
callbacks.lock();

callbacks.add(function(){
    console.log('second');
});

callbacks.fire();

This’ll also log second, but only once; since the object was locked, any further calls to fire will be ignored.