How do I run function inside a class. Javascript

Question

I am having hard time calling a function inside a class. When I started working on this, I had it running, but after making revisions, I cant get it working :((
You can ignore my alerts because I just put them in there to check to see if the function gets called or not.
I have function "Unit" which is a class for me. then I call it by below.
From below code, that new Unit(args) does not get completed. It stops at this.direction=this.setDirection(); and this.setDirection() is not called for some reason. Can anyone take a look and tell me what went wrong?
Thanks!

var teamBlack = [];

var bking = new Unit("black", "king", new Coords(3,1, false));
teamBlack.push(bking);

function Unit(team, type, coords) {

    alert("Unit started " + count);
    this.team = team;
    this.type = type;

    this.position = coords;
    this.highlight = false;
    alert("before setdirection");
    this.direction = this.setDirection();
    alert("this " + this.type);

    this.setDirection = function () {
        alert("setDirection Started ");
        alert(this.type);
        var tempDir = [];
        switch (this.type) {
            case "king" :
                alert("this is king");
                tempDir = [this.N(), this.NW(), this.W(), this.SW(), this.S(), this.SE(), this.E(), this.NE()];
                break;
            case "bishop" :
                tempDir = [this.NW(), this.SW(), this.SE(), this.NE()];
                break;
            case "rook" :
                tempDir = [this.N(), this.S(), this.W(), this.E()];
                break;
            case "pawn" :
            {
                if (this.team == "white") {
                    tempDir = [this.S()];
                } else {
                    tempDir = [this.N()];
                }
                break;
            }
            case "queen" :
            {
                if (this.team == "white") {
                    tempDir = [this.N(), this.W(), this.SW(), this.S(), this.SE(), this.E()];
                } else {
                    tempDir = [this.N(), this.NW(), this.W(), this.S(), this.E(), this.NE()];
                }
                break;
            }

        }
        tempDir = tempDir.filter(function (dir) {
            return dir.x > -1 && dir.x < 3 && dir.y > -1 && dir.y < 4 && dir.c == false;
        });

        return tempDir;
    }
}

You are calling this.setDirection before you have assigned a value to it. You can't do that. Move it to afterward. You may have heard about function declarations being "hoisted", but your assignment to setDirection isn't a declaration, it's a simple assignment of a function to an object property. — RobG
– RobG, Commented Apr 11, 2016 at 5:52

savelichalex · Accepted Answer · 2016-04-11 05:53:24Z

2

This code is wrong because you try call function that is not exist yet in your class. I recommend you to move this function in prototype. For example:

function Unit() {
    //this is your constructor
}

Unit.prototype.setDirection = function() {
    //your code of setDirection function
}

answered Apr 11, 2016 at 5:53

savelichalex

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dz902 · Accepted Answer · 2016-04-11 05:54:58Z

0

Make sure variables are defined, then put this.setDirecton = function()... before calling this.setDirection().

See JSFiddle.

answered Apr 11, 2016 at 5:54

dz902

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Comments

Fidel90 · Accepted Answer · 2016-04-11 06:00:05Z

0

You need to use the setDirection function as a prototype of your Unit class.

Unit.prototype.setDirection = function() {
    //setDirection functionality
}

Within the prototype you have access to your class properties via this.

Check this jsFiddle: https://jsfiddle.net/urtr3quc/

answered Apr 11, 2016 at 6:00

Fidel90

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Comments

Diego Polido Santana · Accepted Answer · 2016-04-11 06:20:10Z

I would improve your code by separating the responsibilities:

//create the class Unit

    function Unit(team, type, coords) {

        alert("Unit started " + count);
        this.team = team;
        this.type = type;

        this.position = coords;
        this.highlight = false;
    }

Then you specify new method for your class:

Unit.prototype.setDirection = function () {
        alert("setDirection Started ");
        alert(this.type);
        var tempDir = [];
        switch (this.type) {
            case "king" :
                alert("this is king");
                tempDir = [this.N(), this.NW(), this.W(), this.SW(), this.S(), this.SE(), this.E(), this.NE()];
                break;
            case "bishop" :
                tempDir = [this.NW(), this.SW(), this.SE(), this.NE()];
                break;
            case "rook" :
                tempDir = [this.N(), this.S(), this.W(), this.E()];
                break;
            case "pawn" :
            {
                if (this.team == "white") {
                    tempDir = [this.S()];
                } else {
                    tempDir = [this.N()];
                }
                break;
            }
            case "queen" :
            {
                if (this.team == "white") {
                    tempDir = [this.N(), this.W(), this.SW(), this.S(), this.SE(), this.E()];
                } else {
                    tempDir = [this.N(), this.NW(), this.W(), this.S(), this.E(), this.NE()];
                }
                break;
            }

        }
        tempDir = tempDir.filter(function (dir) {
            return dir.x > -1 && dir.x < 3 && dir.y > -1 && dir.y < 4 && dir.c == false;
        });
        alert("before setdirection");
        this.direction = tempDir;//setMethod doesn't return thing but set something somewhere
        alert("this " + this.type);
    };

and now you invoke your class instance:

var teamBlack = [];

var bking = new Unit("black", "king", new Coords(3,1, false));
bking.setDirection();
teamBlack.push(bking);

I suggest you to take a look on this link

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