Can I get a jQuery Deferred on document.ready()?

问题:

Right after my script is loaded I am making an Ajax request to get some translations. This should always return after the document is ready since I am loading my scripts at the bottom of the page, but I am still curious if it would be possible to get a Deferred Object on the document ready state.

That way it would be possible to make sure that both, the document is ready and the Ajax call returned successfully before doing anything else, e.g. like this:

$.when( $.ajax('translations'), document.ready())
.then(function(){
    // Start doing stuff here
});

回答1:

You can associate a deferred object with the document using data(), and resolve() it in your ready handler. This way, you should be able to use the stored deferred object with $.when():

$(document).data("readyDeferred", $.Deferred()).ready(function() {
    $(document).data("readyDeferred").resolve();
});

$.when($.ajax("translations"), $(document).data("readyDeferred"))
 .then(function() {
    // Start doing stuff here.
});

回答2:

Here's a cleaned up version of ircmaxell's comment:

(function() {
  var doc_ready = $.Deferred();
  $(doc_ready.resolve);
  $.when(doc_ready, $.ajax('translations')).then(function() {
    console.log("done");
  });
})();

edit

Some clarification to stop the incorrect edits:

Passing a function to the jquery object (e.g. $(some_func)) is the same as $(document).ready(some_func).

Therefore, the $(doc_ready.resolve); line is just shorthand for something like this:

$(document).ready(function() {
  doc_ready.resolve()
});

回答3:

Try this:

$.when($.ajax('translations'), $.ready).then(function() {
    // Start doing stuff here
});

回答4:

My version is:

$.when(
  $.Deferred(function() { $(this.resolve); }), 
  $.ajax('translations')).
  then(function() { console.log("done"); });

回答5:

Update for reference (2015):

This is available in current versions of jQuery:

$.when($.ready).then(...);

It is also simple to convert to a stream using highlandjs:

_($.when($.ready)).map(transform).pipe(output) // etc.

回答6:

jQuery's when is not a proper promise. You can force it into one like this:

function documentReady() {
    return Promise.resolve($.when($.ready));
}

Usage:

documentReady().then(function($) { ... });

It happens to resolve with $ so that's kind of convenient too.

Alternative implementation:

function documentReady() {
    return new Promise(r => $(r));
}