canvas 繪畫隨機點

直接看圖吧；

這樣的隨機點，是小圓點組成的，然后一直在動，記錄一下，萬一以后要用到呢；

canvas的具體設置我就不寫了，另一篇文檔里有；

drawRandomDot () {
  let leftCanvas = this.leftCanvas.nativeElement;
 let leftContext = leftCanvas.getContext("2d");
 let rightCanvas = this.rightCanvas.nativeElement;
 let rightContext = rightCanvas.getContext("2d");
 if(this.dotTimeTicket == null){
 this.dotTimeTicket = setInterval(function(){
 leftContext.clearRect(0,0,280,80);
 for(var i = 0; i < 14; i++){
 for(let j = 0; j < 55; j++){
 let random = Math.ceil(Math.random() * 10);
 if(random > 5){
 leftContext.beginPath();
 leftContext.arc(( 5*(j+1)),( 5*(i+1) ),2,0,2*Math.PI);
 leftContext.fillStyle="rgba(0,192,255,0.65)";
 leftContext.fill();
 leftContext.closePath();
 }
 }
 }
 rightContext.clearRect(0,0,280,30);
 for(var i = 0; i < 6; i++){
 for(let j = 0; j < 55; j++){
 let random = Math.ceil(Math.random() * 10);
 if(random > 5){
 rightContext.beginPath();
 rightContext.arc(( 5*(j+1)),( 5*(i+1) ),2,0,2*Math.PI);
 rightContext.fillStyle="rgba(0,192,255,0.65)";
 rightContext.fill();
 rightContext.closePath();
 }
 }
 }
 },300);
 }
}