Question

I have the following script that dumps a given array’s contents

   function dump(obj) {
            obj = obj || {};
            var result = [];
            $.each(obj, function (key, value) { result.push('"' + key + '":"' + value + '"'); });
            return '{' + result.join(',') + '}';
        }

… but I don’t understand the “array” functions of this. Can you tell me what I need to learn to comprehend what is going within the .each statement?

Update

e.values below is an example of what obj looks like.

Answer 1

This is using jQuery for the each http://api.jquery.com/jQuery.each/ to do the iterating. Here is what happens in your dump function:

function dump(obj) {
    // If 'obj' is falsy then make 'obj' a new Object
    obj = obj || {};

    // Create a new Array
    var result = [];

    // Loop over each property in 'obj' and add
    // "key":"val" String to the 'result' Array,
    $.each(obj, function (key, value) { result.push('"' + key + '":"' + value + '"'); });

    // Join the Array using "," as the delimiter and wrap
    // this with { ... }. Example of arr.join():
    //     var arr = [1, 2, 3];
    //     console.log(arr.join(".")); // "1.2.3"
    //     console.log(arr.join("|")); // "1|2|3"
    return '{' + result.join(',') + '}';
}

Edit
If you need to get the key(s) of an arbitrary Object you can use:

function getKeys(obj) {
    var keys = [],
        i;
    for (var i in obj) {
        if (obj.hasOwnProperty(i)) {
            keys.push(i);
        }
    }
    return keys;
}

var keys = getKeys({key: "value"}); // ["key"]

Here’s a working example.

You could also have a look at Underscore.js’s _.keys().