javascript - 为什么在此代码行中乘以0.002:new Date()。getTime()* 0.002;

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以下代码中乘以0.002有什么特殊用途？

var time = new Date().getTime() * 0.002;

此代码摘录摘自here。我还提供了下面的完整代码：

window.requestAnimFrame = (function(){
  return  window.requestAnimationFrame       ||
          window.webkitRequestAnimationFrame ||
          window.mozRequestAnimationFrame    ||
          window.oRequestAnimationFrame      ||
          window.msRequestAnimationFrame     ||
          function(/* function */ callback, /* DOMElement */ element){
            window.setTimeout(callback, 1000 / 60);
          };
})();
var canvas, context;

init();
animate();

function init() {

canvas = document.createElement( 'canvas' );
canvas.width = 256;
canvas.height = 256;

context = canvas.getContext( '2d' );

document.body.appendChild( canvas );

}

function animate() {
    requestAnimFrame( animate );
    draw();
}

function draw() {
    var time = new Date().getTime() * 0.002;
    var x = Math.sin( time ) * 96 + 128;
    var y = Math.cos( time * 0.9 ) * 96 + 128;

    context.fillStyle = 'rgb(245,245,245)';
    context.fillRect( 0, 0, 255, 255 );

    context.fillStyle = 'rgb(255,0,0)';
    context.beginPath();
    context.arc( x, y, 10, 0, Math.PI * 2, true );
    context.closePath();
    context.fill();
}

最佳答案

该代码使用Math.sin( time ) * 96 + 128作为x坐标，并使用Math.cos( time * 0.9 ) * 96 + 128作为y坐标。如果time是毫秒数（如new Date().getTime()一样），则x坐标和y坐标在每次连续调用时都会剧烈波动，并且该点似乎不会“移动”，而是“跳跃”任意”-每秒六十次，比人眼可以追踪的速度快。将毫秒数乘以0.002会导致点的x坐标和y坐标以更加平滑的方式（以人眼的感觉）振荡。

关于javascript - 为什么在此代码行中乘以0.002:new Date()。getTime()* 0.002; ，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/8321175/