Initializing Array members in Typescript

Question

How do I initialize an array member in the following class.

   class EventObject {
        map:Array;
        constructor() {
            this.map = [];  // error :Cannot convert 'any[]' to  'Array'
            this.map = new Array(); // error :Cannot convert 'any[]' to  'Array'
        };
}

var obj = new EventObject();
console.log(obj.map[0]);

Also, I am able to initialize it if I change the type to number[] . But then, I get an error when I check if it is an instanceof Array :

class EventObject {
            map:number[];
            constructor() {
                this.map = [];
                if(this.map instanceof Array)  //error here
                    alert("Type checking");
            };
}

I want to do both : initialize and check instanceof (or typeof)

How is the Javascript Array different from an array in Typescript ( represented by '[]' ) ?

To answer How is the Javascript Array different from an array in Typescript ( represented by '[]' ) ?, they should be equivalent : typescript.codeplex.com/workitem/812 — basarat
– basarat, Commented Mar 20, 2013 at 5:31

Community · Accepted Answer · 2017-05-23 11:58:11Z

3

map: number[];

Is the correct syntax.

There's several reasons not to use instacenof Array. See here: Check if object is array?

If you want to use instanceof, you must cast the left operator like:

var m: number[];
if (<any>m instanceof Array) {
}

edited May 23, 2017 at 11:58

CommunityBot

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answered Mar 18, 2013 at 16:33

Joseph Lennox

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