180行JavaScript代码实现的小球随机移动代码

Posted 2021-03-05 JerryWangSAP

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<html>
  <body>
  <div id ='desc'><b>test1:</b>test2</div>
  <canvas id = 'canvas'></canvas>    
  </body>
    
  <script>
    window.onload = init();
    function init() {
      canvas = document.getElementById('canvas'); 
      context = canvas.getContext('2d');
      canvas.height = window.innerHeight;
      canvas.width = window.innerWidth;
      mouse = {x:0,y:0};
      colors = [
  '#af0','#7CD14E','#1CDCFF','#FFFF00','#FF0000','#aee137','#bef202','#00b2ff','#7fff24','#13cd4b','#c0fa38','#f0a','#a0f','#0af','#000000' ];
    
      canvas.addEventListener('mousemove',MouseMove,false);
      canvas.addEventListener('mousedown',MouseDown,false);
      canvas.addEventListener('mouseup',MouseUp,false);
      window.addEventListener('resize',canvasResize,false);
      dotsHolder = [];
      mouseMove = false;
      mouseDown = false;
      for(i = 0;i < 100;i++){
          dotsHolder.push(new dots());
      }
    
    /*REQUEST ANIMATION FRAME*/
    (function() {
      var lastTime = 0;
      var vendors = ['ms', 'moz', 'webkit', 'o'];
      for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
          window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];
          window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame']
                                     || window[vendors[x]+'CancelRequestAnimationFrame'];
      }
   
      if (window.requestAnimationFrame)
          window.requestAnimationFrame = function(callback, element) {
              var currTime = new Date().getTime();
              var timeToCall = Math.max(0, 16 - (currTime - lastTime));
              console.log("timetoCall : " + timeToCall);
              var id = window.setTimeout(function() { callback(currTime + timeToCall); },
                timeToCall);
              console.log("id: " + id);
              lastTime = currTime + timeToCall;
              console.log("last time: " + lastTime);
              //return id;
          };
   
      if (!window.cancelAnimationFrame)
          window.cancelAnimationFrame = function(id) {
              clearTimeout(id);
          };
  }());
    
  }
  function canvasResize(event)
  {
   canvas.height = window.innerHeight;
   canvas.width = window.innerWidth;
   cancelAnimationFrame(animate);
    
    
  }
  function MouseUp(event)
    {
      
  if(mouseMove)
  {
    mouseMove = false;}  
      if(mouseDown)
      {
        mouseDown = false;
      }
      
    }
  function MouseDown(event)
    {
      
      mouseDown = true;
      
    }
  function MouseMove(event)
    {
          mouse.x = event.pageX - canvas.offsetLeft;
          mouse.y = event.pageY - canvas.offsetTop;
      if(mouseMove)
      {
       context.lineTo(mouseX,mouseY);
       context.stroke();
        
      }
    }
  function dots(){
   this.xPos = Math.random()*canvas.width;
   this.yPos = Math.random()*canvas.height;
   this.color = colors[Math.floor(Math.random()*colors.length)];
   this.radius = Math.random()*10; 
   this.vx = Math.cos(this.radius);
   this.vy = Math.sin(this.radius);
   this.stepSize = Math.random() / 10;
   this.step = 0;
   this.friction = 7;
   this.speedX = this.vx;
   this.speedY = this.vy;
    
    
  } 

  dots.draw = function()
  {
    
      context.clearRect(0,0,canvas.width,canvas.height);
      for(var c = 0; c < dotsHolder.length;c++)
      {
          dot = dotsHolder[c]; 
          context.beginPath();
          distanceX = dot.xPos - mouse.x;
          distanceY = dot.yPos - mouse.y;
          var particleDistance =  Math.sqrt(distanceX*distanceX + distanceY*distanceY);
          var particleMouse = Math.max( Math.min( 75 / ( particleDistance /dot.radius ), 7 ), 1 );
          context.fillStyle = dot.color;
          dot.xPos += dot.vx;
          dot.yPos += dot.vy;
          if(dot.xPos < -50) {
              dot.xPos = canvas.width+50;
          }
          if(dot.yPos < -50) {
              dot.yPos = canvas.height+50;
          }
          if(dot.xPos > canvas.width+50) {
              dot.xPos = -50;
          }
          if(dot.yPos > canvas.height+50) {
              dot.yPos = -50;
          }
          context.arc(dot.xPos,dot.yPos,(dot.radius/2.5)*particleMouse,0,2*Math.PI,false);
          //console.log("circle x: " + dot.xPos + " y: " + dot.yPos);

          context.fill();
          if(mouseDown) {
          var minimumDistance = 164,
          distance = Math.sqrt((dot.xPos - mouse.x) * (dot.xPos - mouse.x) + (dot.yPos - mouse.y) * (dot.yPos - mouse.y)),
          distanceX = dot.xPos - mouse.x,
          distanceY = dot.yPos - mouse.y; 
          if (distance < minimumDistance) {
              var forceFactor = minimumDistance / (distance * distance),
                  xforce = (mouse.x - dot.xPos) % distance/7,
                  yforce = (mouse.y - dot.yPos) % distance/dot.friction,
                  forceField = forceFactor * 2/dot.friction;
              dot.vx -= forceField * xforce;
              dot.vy -= forceField * yforce;
          }
       
        if(dot.vx > dot.speed) {
            dot.vx = dot.speed/dot.friction; 
            dot.vy = dot.speed/dot.friction;
         
        }
        else if (dot.vy > dot.speed) {
            dot.vy = dot.speed/dot.friction; 
       }
     }

   }
    
  }
  function animate(){
  requestAnimationFrame(animate);
    dots.draw();

  }
  animate();

  </script>
  </html>

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