CODEWITHSUNDEEP
javascriptfunctiontypeerror
Michael
Michael

Reputation: 1

In Javascript, can you call a function of a class within another function of that same class?

EDIT: I've included more detail in the getNeighbor function

I know the following code is long, but I summarized as much as possible. I have the following code creating a hex map:

function Hex (col, row, ter) { //new class of Hexes with row, column, and terrain
  this.col = col;
  this.row = row;
  this.ter = ter; }

function Map (num_col, num_row) { //create a map of Hexes of dimension num_col x num_row
    this.num_col = num_col;
    this.num_row = num_row;
    this.hexArray = new Array();
    for (i=0; i<num_col; i++) {            //creates a 2D array of Hexes with "blank" terrain
        this.hexArray[i] = new Array();
        for (j=0; j<num_row; j++) {
            this.hexArray[i][j] = new Hex(i, j, "blank"); }}

    this.step1 = function() { 
    //assigns a terrain value to 30% of the hexes in the map ("seeds" the map) and returns an array called step1Array whose values are the seeded Hexes.

    this.getNeighbor = function(hex) { //returns all the neighbors of the given hex in an array called neighborArray 
        var delta = [[1, -1, 0], [1, 0, -1], [0, 1, -1],
                 [-1, 1, 0], [-1, 0, 1], [0, -1, 1]];
        this.neighborArray = new Array();

        for (i=0; i<delta.length; i++) {
            //get the coordinates of the neighbors and store them as newCol and newRow
            if (newCol<0 || newRow<0 || newCol>this.num_col-1 || newRow>this.num_row-1  //skip any hexes that are out of bounds
                || this.hexArray[newCol][newRow].ter !== "blank") continue;             //or that are already seeded
            this.neighborArray.push(this.hexArray[newCol][newRow]); }

    return this.neighborArray;
}

    this.step2 = function() { //assigns a terrain value to all "blank" neighbors of the seeded hexes
        for (i=0; i<this.step1Array.length; i++) {
            this.getNeighbor(this.step1Array[i]);
            if (this.neighborArray.length === 0) continue;  //if there are no "blank" neighbors, continue to the next seeded Hex
            else {
                for (j=0; j<this.neighborArray.length; j++) {    //else assign each blank neighbor a terrain value
                        var percent = Math.random();
                        var temp_col = this.neighborArray[i].col;
                        var temp_row = this.neighborArray[i].row;
                //based on the value of "percent", assign this.hexArray[temp_col][temp_row].ter a given value
                 }
            }
        }
   }

var testMap = new Map(3,3) //create a 3x3 map of hexes
testMap.step1();           //seed the map
testMap.step2();           //assign terrain values to neighbors of seeded hexes. get error.

My problem is that I get the following error when compiling: Uncaught TypeError: Cannot read property 'col' of undefined

I've experimented a lot with the step1 and getNeighbor functions, and they return accurate arrays of Hexes, so I don't think those are the problem.

I can't figure out what the problem is. Is there a problem with calling the getNeighbor function within the step2 function? for some reason it doesn't like

var temp_col = this.neighborArray[i].col;

Upvotes: 0

Views: 70

Answers (1)

Agent96
Agent96

Reputation: 475

It may be that your 'this' is not the 'this' you think it is as you are in an inner function.

You could try:

var _this = this;  //Create a local variable containing this
this.step2 = function() { //assigns a terrain value to all "blank" neighbors of the seeded hexes
    for (i=0; i<this.step1Array.length; i++) {
        _this.getNeighbor(this.step1Array[i]);  //use _this instead of this
        if (_this.neighborArray.length === 0) continue;

Upvotes: 1

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