javascript literal initialisation loop

Question

I have an object which has several properties that are set when the object is created.

This object recently changed to object literal notation, but I've hit a bit of a problem that searching on the net doesn't reveal.

Simply stated I need to do this:

Star = function(_id, _x, _y, _n, _o, _im, _c, _b, _links) {
    var self = {
        id: _id,
        // other properties
        links: [],
        for (var i=0,j=0;i<8;i++) { //<- doesn't like this line
            var k = parseInt(_links[i]);
            if (k > 0) {
                this.links[j++] = k;
            }
        },
        // other methods
    };
    return self;
};

How do I initialise a property in the constructor in object literal notation?

Answer 1

You can't. Object notation doesn't allow this. However, you can add the properties AFTER initializing your object.

By the way, self is a defined object already, which is an alias for the window object. While you ARE defining a temporary object named self [and thus, you aren't getting rid of window.self] this isn't something you shold be doing. Act as if self was a keyword and your current usage of it is illegal.

Answer 2

1. You can create the array on the fly using an anonymous function:

   Star = function(_id, _x, _y, _n, _o, _im, _c, _b, _links) {
       var self = {
           id: _id,
           // other properties
           links: (function() {
               var a = [];
               for (var i=0;i<8;i++) {
                   var k = parseInt(_links[i]);
                   if (k > 0) {
                       a.push(k);
                   }
               }
               return a;
           })(),
           // other methods
       };
       return self;
   };
   

2. You can do it after the literal is defined:

   Star = function(_id, _x, _y, _n, _o, _im, _c, _b, _links) {
       var self = {
           id: _id,
           // other properties
           links: [],
           // other methods
       };
       for (var i=0,j=0;i<8;i++) {
           var k = parseInt(_links[i]);
           if (k > 0) {
               self.links[j++] = k;
           }
       }
       return self;
   };
   

Answer 3

For this specific example, you could use an anonymous function, like this:

Star = function(_id, _x, _y, _n, _o, _im, _c, _b, _links) {
    var self = {
        id: _id,
        // other properties
        links: (function(){
            var links = [];
            for (var i=0;i<8;i++) {
                var k = parseInt(_links[i]);
                if (k > 0) {
                    links.push(k);
                }
            }
            return links;
        })(),
        // other methods
    };
    return self;
};