Typescript - initialize a 2D array ERROR

Question

I'm trying to create a 2D array for coordinates like [[x_1,y_1,z_1], [x_2,y_2,z_2], [...],...].

Here is my code for initialization and initial declaration:

var ALLcoordinates:number[][];

for (var i=0; i< dims; i++) {
    ALLcoordinates[i]=[];
    for (var j=0; j<chainSize; j++){
        ALLcoordinates[i][j]=0;
    }
}

After that, I assign new values for each row in this loop :

for (var i = 0; i < chainSize; i++) {
    var alea1 = Math.floor(Math.random()*(3-0+1))+0;
    var alea2 = Math.floor(Math.random()*(3-0+1))+0;
    var alea3 = Math.floor(Math.random()*(3-0+1))+0;
    var coordinates:number[];
    coordinates = [alea1,alea2,alea3];
    ALLcoordinates[i]=coordinates;

}

But when I compile it, I get this error Uncaught TypeError: Cannot set property '0' of undefined for this line ALLcoordinates[i] = [];

I would appreciate any help, thanks

Is this typescript or javascript? This is not the right way to declare variables in typescript. — Koby Douek
– Koby Douek, Commented Jun 14, 2017 at 9:25

Koby Douek · Accepted Answer · 2017-06-14 09:28:28Z

7

Declaring an array does not initialize it.

You are missing the ALLcoordinates initialization:

var ALLcoordinates:number[][];

ALLcoordinates = [];            //  ◄ initialize the array

for (var i=0; i< dims; i++) {
    ALLcoordinates[i]=[];
    for (var j=0; j<chainSize; j++){
        ALLcoordinates[i][j]=0;
    }
}

answered Jun 14, 2017 at 9:28

Koby Douek

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Saravana · Accepted Answer · 2017-06-14 09:27:57Z

6

When you did var ALLcoordinates:number[][];, you did not initialize it with any value. You just specified its type. It will still be undefined at runtime. So undefined[0] throws the error. Initialize it before using it:

var ALLcoordinates: number[][] = [];

answered Jun 14, 2017 at 9:27

Saravana

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