在学习canvas 菜鸟一个 写的一个小demo
HTML
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>刮刮乐</title>
<style type="text/css">
* {
margin: 0;
padding: 0;
}
#clock {
width: 500px;
height: 200px;
text-align: center;
line-height: 200px;
font-size: 36px;
letter-spacing: 10px;
}
#myCanvas {
position: absolute;
top: 0;
left: 0%;
}
</style>
</head>
<body>
<div id="clock">
<canvas id="myCanvas" width="500" height="200"></canvas>
<div id="content">谢谢惠顾</div>
</div>
<script src="./index.js"></script>
<script>
new Canvas({
el:'#clock',
data:{
x:0,
y:0,
drawingWidth:5,
drawingHeigth:5,
background:'gray'
}
})
</script>
</body>
</html>
js
function Canvas(option) {
this.init(option)
}
Canvas.prototype = {
init: function (options) {
this.initData(options);
console.log(2)
},
注意这里的this是指向当前的原型的 和 外面的数据是没有任何关系的 这里修改了他的this 那么这里面的this数据就指向了当前修改的this 和外面是没关系的 [注意 注意 注意]
initData: function (options) {
this.canvas = document.getElementById('myCanvas')
this.ctx = this.canvas.getContext("2d");
this.width = this.canvas.width
this.height = this.canvas.height
this.x = options.data.x
this.y = options.data.y
this.drawingWidth = options.data.drawingWidth
this.drawingHeigth = options.data.drawingHeigth
this.ctx.rect(this.x, this.y, this.width, this.height)
this.ctx.fillStyle = options.data.background;
this.ctx.fill()
this.canvasEvent()
this.changeFont()
},
canvasEvent:function(){
this.canvas.onmousedown = ()=>{
this.canvas.onmousemove = (e)=>{
if(e.clientX == this.width - 1 || e.clientY == this.height - 1){
this.canvas.onmousemove = null
return
}
this.ctx.clearRect(e.clientX,e.clientY,this.drawingWidth,this.drawingHeigth)
}
}
this.canvas.onmouseup = ()=>{
this.canvas.onmousemove = null
return
}
},
changeFont:function(){
var arr = ['今天学习javascript', '今天学习node', '今天学习vue', '今天学习react', '今天学习typeScript', '今天学习小程序', '今天学习html', '今天学习css']
var n = Math.floor(Math.random() * arr.length)
if (n < 2) {
n = arr.length - 1
}
document.getElementById('content').innerHTML = arr[n]
}
}
