For-in loop in TypeScript always treats variable like a string [duplicate]

Question

This is something that has been bugging me for a while now. In TypeScript, if I define a for-in loop my variable is always treated as a string. Example:

for(var room in this.rooms) {
    room.placement.x = 52;
}

The room.placement.x will fail because it treats room as a string. this.rooms is actually a collection of Room objects, but room is not a Room... it's a string.

Is this a TypeScript version issue or something that is sticking around? It's highly frustrating.

Is there a way to define room so that TypeScript can treat it like a Room?

The definition of rooms is: private rooms: Room.Game.Room[];

It's an array of custom objects.

while this may be a duplicate question, the answer provided by Bruno is unique and is exactly what I needed. — BrianLegg
– BrianLegg, Commented Aug 15, 2016 at 15:49

Matthias Braun · Accepted Answer · 2023-02-22 19:16:23Z

20

If this.rooms is an array, the proper syntax is for ...of:

for (let room of this.rooms) {
    room.placement.x = 52;
}

for ... in iterates over the keys.

See this for more.

edited Feb 22, 2023 at 19:16

Matthias Braun

34.8k27 gold badges158 silver badges177 bronze badges

answered Aug 15, 2016 at 15:34

Bruno Grieder

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1 Comment

BrianLegg Over a year ago

This is exactly what I was looking for. Thank you. I will accept your answer when the timer lets me.

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