Game Score
Push the buttons to move the red square:
Count The Score
There are many ways to keep the score in a game, we will show you how to write a score onto the canvas.
First make a score component:
Example
var myGamePiece;
var myObstacles = [];
var myScore;
function startGame() {
myGamePiece = new component(30, 30, "red", 10, 160);
myScore = new component("30px", "Consolas", "black",
280,
40, "text");
myGameArea.start();
}
The syntax for writing text on a canvas element is different from drawing a rectangle. Therefore we must call the component constructor using an additional argument, telling the constructor that this component is of type "text".
In the component constructor we test if the component is of type "text", and use the
fillText method instead of the fillRect method:
Example
function
component(width, height, color, x, y, type)
{
this.type = type;
this.width = width;
this.height = height;
this.speedX = 0;
this.speedY =
0;
this.x = x;
this.y = y;
this.update =
function() {
ctx = myGameArea.context;
if (this.type == "text") {
ctx.font =
this.width + " " + this.height;
ctx.fillStyle = color;
ctx.fillText(this.text, this.x, this.y);
} else {
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
}
...
}
At last we add some code in the updateGameArea function that writes the score
onto the canvas. We use the frameNo property to count the score:
Example
function updateGameArea() {
var x, height, gap, minHeight, maxHeight,
minGap, maxGap;
for (i = 0; i < myObstacles.length; i +=
1) {
if
(myGamePiece.crashWith(myObstacles[i])) {
myGameArea.stop();
return;
}
}
myGameArea.clear();
myGameArea.frameNo += 1;
if (myGameArea.frameNo == 1 ||
everyinterval(150)) {
x =
myGameArea.canvas.width;
minHeight = 20;
maxHeight = 200;
height = Math.floor(Math.random()*(maxHeight-minHeight+1)+minHeight);
minGap = 50;
maxGap = 200;
gap = Math.floor(Math.random()*(maxGap-minGap+1)+minGap);
myObstacles.push(new component(10, height, "green", x, 0));
myObstacles.push(new component(10, x - height - gap, "green", x,
height + gap));
}
for (i = 0; i
< myObstacles.length; i += 1) {
myObstacles[i].speedX = -1;
myObstacles[i].newPos();
myObstacles[i].update();
}
myScore.text="SCORE: " + myGameArea.frameNo;
myScore.update();
myGamePiece.newPos();
myGamePiece.update();
}
Try it Yourself »
