drawing circle functions in canvas

Question

i need to draw a circle. it is probably simple and there may be tons of tutorials out there, but i cant find one for my spicific problem. i need to tell it to draw a circle from here:

function startGame() {
//circle needs to be called from here.

//this is how i draw a square
 square = new component(40, 40, "blue", 10, 10);
myGameArea.start();

}

and then i need to actually draw it from here:

function component(width, height, color, x, y) {
    this.width = width;
    this.height = height;
    this.speedX = 0;
    this.speedY = 0;    
    this.x = x;
    this.y = y;    
  //this is where it draws the stuff
    this.update = function() {
        var ctx = myGameArea.context;
        ctx.fillStyle = color;
        ctx.fillRect(this.x, this.y, this.width, this.height);
    }
    this.newPos = function() {
        this.x += this.speedX;
        this.y += this.speedY;        
    }    
    

}

this function is currently programmed to draw squares and not circles. i need to be able to draw and re-draw circles from there. if i create a new funtion, it needs to use the function this.update, and that would overwrite the current one. i need to use it to update game assets, like exampleSquare.update().

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.frameNo = 0;
        this.interval = setInterval(updateGameArea, 20);
        },
    clear : function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}

this calls the

function updateGameArea() {
myGameArea.clear();
  }

whitch i left empty for sake of simplicity. if you need my full code you can find it here: https://game.octopuscat.repl.co/ it is kinda messy and has a lot of unimplemented stuff so this is a simplifyed version.

user_18600833 · Answer

Add a specifier to the component function. For example you can use a string as the first parameter that defines if you want to draw a circle or square:

function component(type, width, height, color, x, y) {
     if(type == "square") {
     ...
     //draw
     } else if(type == "circle") {
     ... 
     //draw
     }
}

And then you can repurpose the parameters if its a circle

... if(type == "circle") {
     var radius = width
     var diameter = height
     //draw
}

drawing circle functions in canvas

1 Answers