enemies.js

class Enemy
{
    constructor()
    {
        this.frameX=0;
        this.frameY=0;
        this.fps=30;
        this.frameInterval=1000/this.fps;
        this.frameTimer=0;
        this.delete=false;
    }

    update(deltaTime)
    {
        //movement
        this.x-=this.speedX+ this.game.speed;
        this.y+=this.speedY;
        if(this.frameTimer>this.frameInterval)
        {
            this.frameTimer=0;
            if(this.frameX<this.maxFrame)
                this.frameX++;
            else 
                this.frameX=0;
        }
        else 
        {
            this.frameTimer+=deltaTime;
        }

        //if off screen or not
        if(this.x+this.width<0)
            this.delete=true;
    }

    draw(context)
    {
        if(this.game.debug)
            context.strokeRect(this.x,this.y,this.width,this.height);
        context.drawImage(this.image, this.frameX*this.width , 0 , this.width , this.height , this.x , this.y , this.width , this.height);
    }
}

export class FlyingEnemy extends Enemy
{
    constructor(game)
    {
        super();
        this.game=game;
        this.width=60;
        this.height=44;
        this.x=this.game.width + Math.random()*this.game.width*0.5;
        this.y=Math.random()*this.game.height*0.5;
        this.speedX=Math.random()+1;
        this.speedY=0;
        this.maxFrame=5;
        this.image=document.getElementById("enemy_fly");
        this.angle=0;
        this.va=Math.random()*0.1+0.1;
    }
    update(deltaTime)
    {
        super.update(deltaTime);
        this.angle+=this.va;
        this.y+=Math.sin(this.angle);
    }
}

export class GroundEnemy extends Enemy
{
    constructor(game)
    {
        super();
        this.game=game;
        this.width=60;
        this.height=87;
        this.x=this.game.width;
        this.y=this.game.height - this.height - this.game.groundMargin;
        this.image=document.getElementById("enemy_plant");
        this.speedX=0;
        this.speedY=0;
        this.maxFrame=1;
    }
}

export class ClimbingEnemy extends Enemy
{
    constructor(game)
    {
        super();
        this.game=game;
        this.width=120;
        this.height=144;
        this.x=this.game.width;
        this.y=Math.random()*this.game.height*0.5;
        this.image=document.getElementById("enemy_spider");
        this.speedX=0;
        this.speedY=Math.random()>0.5?1:-1;
        this.maxFrame=5;
    }
    update(deltaTime)
    {
        super.update(deltaTime);
        if(this.y>this.game.height-this.height-this.game.groundMargin)
            this.speedY*=-1;
        if(this.y<-this.height)
            this.delete=true;
    }
    draw(context)
    {
        super.draw(context);
        context.beginPath();
        context.moveTo(this.x+this.width/2,0);
        context.lineTo(this.x+this.width/2,this.y+50);
        context.stroke();
    }
}