Looping through array of arrays... why won't this work?

Question

I'd like to loop through data from two arrays to check if any of the data's distance is close to the player.

Container arrays (only 1 element in each right now):

peopleContainers_Array.push(peopleContainer);
animalContainers_Array.push(animalContainer);

I've loaded two arrays of create js containers into NPC_Array:

NPC_Array.push(peopleContainers_Array, animalContainers_Array);

And would like to loop through both as such to get the x,y values of data elements in the container arrays.

for (npc_array in NPC_Array) {
     //NPC_Array(peopleContainers_Array, animalContainers_Array);
    for (container in NPC_Array[npc_array]) {
        console.log(NPC_Array[npc_array[container].x]); //outputs undefined
    }
}

Why wouldn't this work?

Thanks!

Side note: You may want to read through "[Why is using “for…in” with array iteration such a bad idea?](http://stackoverflow.com/q/500504)" — Jonathan Lonowski, Aug 14 '13 at 03:05

Fly_pig · Accepted Answer · 2013-08-15T02:22:50.837

1

for (npc_array in NPC_Array) {
     //NPC_Array(peopleContainers_Array, animalContainers_Array);
    for (container in NPC_Array[npc_array]) {
        console.log(NPC_Array[npc_array][container].x);
    }
}

I think it should be like this.

Well,replace for ... in:

for (var index=0;index<NPC_Array.length;index++) {
     //NPC_Array(peopleContainers_Array, animalContainers_Array);
    for (var childIndex=0;childIndex<NPC_Array[index].length;childIndex++) {
        console.log(NPC_Array[index][childIndex]['x']);
    }
}

edited Aug 15 '13 at 02:22

answered Aug 14 '13 at 03:01

Fly_pig

155
8

Aside from using a `for...in` loop when a regular `for` loop, yes. – Matt Ball Aug 14 '13 at 03:12
@MattBall What's wrong with using `for...in`? I want to get the objects within an array; isn't that what it's used for? Maybe I don't know the difference of when to use `for...in` vs `for` – user3871 Aug 14 '13 at 03:22
3

@Growler [scroll up.](http://stackoverflow.com/questions/18222519/looping-through-array-of-arrays-why-wont-this-work/18222548?noredirect=1#comment26712856_18222519) – Matt Ball Aug 14 '13 at 03:43
@Growler `for...in` is used to iterate members of objects rather than array, if did it, unpredictable issues may come up.See the [link](http://stackoverflow.com/questions/500504/why-is-using-for-in-with-array-iteration-such-a-bad-idea) Jonathan Lonowski gave in the comment. – Fly_pig Aug 14 '13 at 03:44

Looping through array of arrays... why won't this work?

1 Answers1