Question

Okay, so this is complicated so try to bear with me, i will try to keep it as simple as possible:

I have a “class” Struct, that creates a “struct like” skeleton to apply to ArrayBuffers within Javascript. The problem is when I am attempting to mimic the ‘c’ like behavior of allowing a struct to contain other structs.

The problem is that it clobbers the iterator of the calling method (obviously a closure problem), that i cant seem to figure out.

Here is an example of the code that gets clobbered (hopefully this is enough code to get the answer, if not I will add more as necessary, just trying to keep extraneous code out of here):

function StructObject(){
this.applyBuf = function(buf, start){
   var struct = {};
   for (obj in this){
       //problem is here:
       console.log(obj); //prints "c" on the way in
       struct[obj] = this[obj].__createFromBuf();
       console.log(obj); //prints "foo" (see the structs below)
   }
   return struct;
 }
}


function struct(strctObj, name){
var structObject = new StructObject();
...
//create the skeleton
for (item in strctObj){
//the specific code that fails me
structObject[item].__createFromBuf = function(buf, pos){
            return structs[this.name].applyBuf(buf, pos);
}
...
//store the skeleton for later application
structs[name] = structObject;
}


//Creating structs looks like this:
new struct({ foo: type.INT }, "bar");
new struct({
   a: type.INT, //defines size of memory (like c's sizeof)
   b: type.LONG,
   c: {type: type.STRUCT, name: "bar"},
   d: type.SHORT}, "myStruct");

structs.myStruct.applyBuf(new ArrayBuffer(35));

When I iterate through the first struct on the class method applyBuf, it calls __createFromBuf on each item within the struct skeleton, if the item is another struct __createFromBuf calls applyBuf on the other “struct skeleton” object and returns an instance of that struct back to the calling struct, which works as intended.

JSFIDDLE — Here is the link to a working example 🙂

Answer 1

clean your for statements:

if not declared properly, the for loop index becomes a global member.

demonstration:

for (item in strctObj) // item becomes a global member

for (var item in strctObj) // item is scoped within the loop's owner function