Aidan Edwards Aidan Edwards - 2 months ago 18
Javascript Question

Return array from function

--Solved by Elliot B. Thanks!
May also take int account the other modifications.

Here is the result. Thanks, everyone, for the speedy answers! http://dl.dropbox.com/u/18785762/Rust/index.html

I'm writing a game in javascript, and I want to keep the files for matching block IDs to files in a seperate .js file from the map compiler, so that I can edit things easily. However, the IDs are stored in an array, and I can't seem to get it to use the return function properly. Any help?

drawmap.js:

function drawmap() {

var images = BlockID();

var level = [
"ssssssssssssssssssssss",
"sgggggggggCCCCCdddddss",
"ssssssssss sssssss"
];

var top = 100;
var left = 100;
var mytop = top;
var myleft = left;
for (y=0; y<level.length; ++y) {
var row = level[y];
for (x=0; x < row.length; ++x) {
var c = row.charAt(x);
if(c != ' ') {
img_create(images[c], mytop, myleft);
}
mytop += 13;
myleft += 27;
}
mytop = top + (y+1)*13;
myleft = left - (y+1)*27;
}
}


mapread.js:

function BlockID() {
var IDs = new Array();
images['s'] = "Images/Block_01.png";
images['g'] = "Images/Block_02.png";
images['C'] = "Images/Block_03.png";
images['d'] = "Images/Block_04.png";
return IDs;
}

Answer

At a minimum, change this:

function BlockID() {
    var IDs = new Array();
        images['s'] = "Images/Block_01.png";
        images['g'] = "Images/Block_02.png";
        images['C'] = "Images/Block_03.png";
        images['d'] = "Images/Block_04.png";
    return IDs;
}

To this:

function BlockID() {
    var IDs = new Object();
        IDs['s'] = "Images/Block_01.png";
        IDs['g'] = "Images/Block_02.png";
        IDs['C'] = "Images/Block_03.png";
        IDs['d'] = "Images/Block_04.png";
    return IDs;
}

There are a couple fixes to point out. First, images is not defined in your original function, so assigning property values to it will throw an error. We correct that by changing images to IDs. Second, you want to return an Object, not an Array. An object can be assigned property values akin to an associative array or hash -- an array cannot. So we change the declaration of var IDs = new Array(); to var IDs = new Object();.

After those changes your code will run fine, but it can be simplified further. You can use shorthand notation (i.e., object literal property value shorthand) to create the object and return it immediately:

function BlockID() {
    return {
            "s":"Images/Block_01.png"
            ,"g":"Images/Block_02.png"
            ,"C":"Images/Block_03.png"
            ,"d":"Images/Block_04.png"
    };
}
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