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How to achieve collision and rebound of multiple balls through JS

亚连Original: 2018-06-08 16:16:182468browse

This article mainly introduces the native JS to realize the collision and rebound effect of multiple small balls, and analyzes the related numerical calculation, random number generation, event response and other operation skills of JavaScript to realize the small ball collision in the form of a complete example. Friends who need it can Refer to the following

example of this article describing the native JS to achieve the collision and rebound effect of multiple small balls. Share it with everyone for your reference, the details are as follows:

Implementation ideas: The movement of the ball is changed by changing the left and top values of the ball. The coordinates are (x, y) )When the x/y value is added to the maximum, that is, when it is added to the width or height of the parent, the x value or y value is reduced. Similarly, when the x value or y value is reduced to the minimum, the x value or y value is also reduced. In addition, the above ideas can realize the rebound of the ball when it hits the wall.

The collision between the ball and the ball needs to determine which direction the ball is being hit, so as to determine which direction the ball should move. , also change the coordinate value of the ball to realize the rebound of the ball

Implementation code:

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>小球碰撞</title>
    <style type="text/css">
      * {
        margin: 0;
        padding: 0;
      }
      #wrap {
        height: 800px;
        width: 1300px;
        border: 1px solid red;
        /*小球设置相对定位*/
        position: relative;
        margin: 0 auto;
        overflow: hidden;
      }
      p {
        width: 40px;
        height: 40px;
        border-radius: 50%;
        background-color: red;
        position: absolute;
        top: 0;
        left: 0;
        color: white;
        font-size: 25px;
        text-align: center;
        line-height: 40px;
      }
    </style>
  </head>
  <body>
    <p id="wrap">
    </p>
  </body>
  <!--<script src="js/common.js" type="text/javascript" charset="utf-8"></script>-->
  <script type="text/javascript">
    /**
     * 生成并返回一个从m到n全区间的随机数
     * @param {Object} m
     * @param {Object} n
     */
    function randomNum(m, n) {
      return Math.floor(Math.random() * (n - m + 1) + m);
    }
    /**
     * 生成一个随机颜色，并返回rgb字符串值
     */
    function randomColor() {
      var r = randomNum(0, 255);
      var g = randomNum(0, 255);
      var b = randomNum(0, 255);
      return "rgb(" + r + "," + g + "," + b + ")";
    }
    //获得wrapp
    var wrapp = document.getElementById("wrap");
    //定义数组存储所有的小球
    var balls = [];
    //生成小球函数
    function createBalls() {
      for (var i = 0; i < 20; i++) {
        var ball = document.createElement("p");
        //随机小球起始的X坐标和小球的Y坐标
        ball.x = randomNum(0, 1200);
        ball.y = randomNum(0, 700);
        //随机小球的移动速度
        ball.speed = randomNum(2, 5);
        //随机小球移动的方向
        if (Math.random() - 0.5 > 0) {
          ball.xflag = true;
        } else {
          ball.xflag = false;
        }
        if (Math.random() - 0.5 > 0) {
          ball.yflag = true;
        } else {
          ball.yflag = false;
        }
        //随机小球的背景颜色
        ball.style.backgroundColor = randomColor();
        ball.innerHTML = i + 1;
        //将小球插入当wrapp中
        wrapp.appendChild(ball);
        //将所有的小球存储到数组中
        balls.push(ball);
      }
    }
    createBalls();
    //小球移动函数，判断小球的位置
    function moveBalls(ballObj) {
      setInterval(function() {
        ballObj.style.top = ballObj.y + "px";
        ballObj.style.left = ballObj.x + "px";
        //判断小球的标志量，对小球作出相应操作
        if (ballObj.yflag) {
          //小球向下移动
          ballObj.y += ballObj.speed;
          if (ballObj.y >= 800 - ballObj.offsetWidth) {
            ballObj.y = 800 - ballObj.offsetWidth;
            ballObj.yflag = false;
          }
        } else {
          //小球向上移动
          ballObj.y -= ballObj.speed;
          if (ballObj.y <= 0) {
            ballObj.y = 0;
            ballObj.yflag = true;
          }
        }
        if (ballObj.xflag) {
          //小球向右移动
          ballObj.x += ballObj.speed;
          if (ballObj.x >= 1300 - ballObj.offsetHeight) {
            ballObj.x = 1300 - ballObj.offsetHeight;
            ballObj.xflag = false;
          }
        } else {
          //小球向左移动
          ballObj.x -= ballObj.speed;
          if (ballObj.x <= 0) {
            ballObj.x = 0;
            ballObj.xflag = true;
          }
        }
        crash(ballObj);
      }, 10);
    }
    var x1, y1, x2, y2;
    //碰撞函数
    function crash(ballObj) {
      //通过传过来的小球对象来获取小球的X坐标和Y坐标
      x1 = ballObj.x;
      y1 = ballObj.y;
      for (var i = 0; i < balls.length; i++) {
        //确保不和自己对比
        if (ballObj != balls[i]) {
          x2 = balls[i].x;
          y2 = balls[i].y;
          //判断位置的平方和小球的圆心坐标的关系
          if (Math.pow(x1 - x2, 2) + Math.pow(y1 - y2, 2) + 800 <= Math.pow(ballObj.offsetWidth + balls[i].offsetWidth, 2)) {
            //判断传过来的小球对象，相对于碰撞小球的哪个方位
            if (ballObj.x < balls[i].x) {
              if (ballObj.y < balls[i].y) {
                //小球对象在被碰小球的左上角
                ballObj.yflag = false;
                ballObj.xflag = false;
              } else if (ballObj.y > balls[i].y) {
                //小球对象在被碰小球的左下角
                ballObj.xflag = false;
                ballObj.yflag = true;
              } else {
                //小球对象在被撞小球的正左方
                ballObj.xflag = false;
              }
            } else if (ballObj.x > balls[i].x) {
              if (ballObj.y < balls[i].y) {
                //小球对象在被碰撞小球的右上方
                ballObj.yflag = false;
                ballObj.xflag = true;
              } else if (ballObj.y > balls[i].y) {
                //小球对象在被碰撞小球的右下方
                ballObj.xflag = true;
                ballObj.yflag = true;
              } else {
                //小球对象在被撞小球的正右方
                ballObj.xflag = true;
              }
            } else if (ballObj.y > balls[i].y) {
              //小球对象在被撞小球的正下方
              ballObj.yflag = true;
            } else if (ballObj.y < balls[i].y) {
              //小球对象在被撞小球的正上方
              ballObj.yflag = false;
            }
          }
        }
      }
    }
    for (var i = 0; i < balls.length; i++) {
      //将所有的小球传到函数中,来实现对小球的移动
      moveBalls(balls[i]);
    }
  </script>
</html>

Operation effect:

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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