jQuery: load scripts in order

Question

I'm trying load some scripts dynamically with jQuery:

var scripts = ['script1.js','script2.js','script3.js'];

$.each(scripts , function(i, val) {
     $.getScript(val, function() {
     console.log('loaded '+ val);
});

But sometimes the order of loaded scripts changes. How can I load each script after the previous one has successfully loaded?

Answer 1

You can load each after the previous has finished loading by using the callback function of $.getScript() as a recursive function call.

//setup array of scripts and an index to keep track of where we are in the process
var scripts = ['script1.js','script2.js','script3.js'],
    index   = 0;

//setup a function that loads a single script
function load_script() {

    //make sure the current index is still a part of the array
    if (index < scripts.length) {

        //get the script at the current index
        $.getScript(scripts[index], function () {

            //once the script is loaded, increase the index and attempt to load the next script
            console.log('Loaded: ' + scripts[index]);
            index++;
            load_script();
        });
    }
}

What's occurring in your code is that the scripts are being requested at the same time and since they load asynchronously, they return and execute in random order.

Update

I haven't tested this, but if the scripts are hosted locally, then you could try to retrieve them in plain text, then store all of the code in variables until they are all loaded at which time you could evaluate the scripts in order:

var scripts   = ['script1.js','script2.js','script3.js'],

    //setup object to store results of AJAX requests
    responses = {};

//create function that evaluates each response in order
function eval_scripts() {
    for (var i = 0, len = scripts.length; i < len; i++) {
        eval(responses[scripts[i]]);
    }
}

$.each(scripts, function (index, value) {
    $.ajax({
        url      : scripts[index],

        //force the dataType to be `text` rather than `script`
        dataType : 'text',
        success  : function (textScript) {

            //add the response to the `responses` object
            responses[value] = textScript;

            //check if the `responses` object has the same length as the `scripts` array,
            //if so then evaluate the scripts
            if (responses.length === scripts.length) { eval_scripts(); }
        },
        error    : function (jqXHR, textStatus, errorThrown) { /*don't forget to handle errors*/ }
    });
});