进行异步jQuery调用

Question

$(document).ready(function(){

  $.getJSON("https://api.deckbrew.com/mtg/sets", function(sets) {
    $(sets).each(function() {
      $('<div id="' + this.name + '" class="set"/>')
      .text(this.name)
      .appendTo("#collection");

    });
  });

  $.getJSON("https://api.deckbrew.com/mtg/cards", function(cards) {
    $(cards).each(function(){
      $('<div id="' + this.name + '" class="card"/>')
      .text(this.name)
      .appendTo("#" + this.editions[0].set);

    });
  });

});

I was wondering how I might (without using ajax and sticking to the "getJSON" method) make the two calls happen asynchronously. I can't make anything useful happen with the second jQuery object; I believe that's because of the synchronous nature of the calls. How can I make them work in order?

Answer 1

If you want these to happen in order, then you need to specifically serialize them and using the built-in promises that getJSON() returns is a simple way to do that:

$(document).ready(function () {
    $.getJSON("https://api.deckbrew.com/mtg/sets").then(function (sets) {
        $(sets).each(function () {
            $('<div id="' + this.name + '" class="set"/>')
                .text(this.name)
                .appendTo("#collection");
        });
    }).then(function () {
        $.getJSON("https://api.deckbrew.com/mtg/cards").then(function (cards) {
            $(cards).each(function () {
                $('<div id="' + this.name + '" class="card"/>')
                    .text(this.name)
                    .appendTo("#" + this.editions[0].set);
            });
        });
    });
});

Or, a little faster (end to end time) would be to launch both requests at the same time and then process the results in order. Again using jQuery promises to manage this:

$(document).ready(function(){
    $.when(
        $.getJSON("https://api.deckbrew.com/mtg/sets"), 
        $.getJSON("https://api.deckbrew.com/mtg/cards")
    ).then(function(r1, r2) {
        // process sets
        var sets = r1[0];
        $(sets).each(function() {
          $('<div id="' + this.name + '" class="set"/>')
          .text(this.name)
          .appendTo("#collection");
        });

        // process cards
        var cards = r2[0];
        $(cards).each(function(){
          $('<div id="' + this.name + '" class="card"/>')
          .text(this.name)
          .appendTo("#" + this.editions[0].set);
        });
    });
});

This last scheme uses $.when() to tell us when both ajax calls are done and it also sequences the results for us, regardless of which one actually finished first.

Answer 2

To run the getJSONS's in sequence, run the second in the callback of the first

like so

$(document).ready(function() {
    $.getJSON("https://api.deckbrew.com/mtg/sets", function(sets) {
        $(sets).each(function() {
            $('<div id="' + this.name + '" class="set"/>')
                .text(this.name)
                .appendTo("#collection");
        });
        $.getJSON("https://api.deckbrew.com/mtg/cards", function(cards) {
            $(cards).each(function() {
                $('<div id="' + this.name + '" class="card"/>')
                    .text(this.name)
                    .appendTo("#" + this.editions[0].set);
            });
        });
    });
});

personally, I would go with @jfriend00's promise method - I was going to add that to this answer, but he answered in the meantime, so, go with that more flexible method

Answer 3

EDIT Since you said you were trying to use call both getJSON methods in order, then you can make the second call work after the first by using the DOMNodeInserted event

Well maybe a solution would be to use DOMNodeInserted event since you are appending to #collection

so:

$("#collection").on('DOMNodeInserted',function(){

    $.getJSON...
});

According to DOCS

DOMNodeInserted

Fired when a node has been added as a child of another node. This event is dispatched after the insertion has taken place. The target of this event is the node being inserted.