前端之家收集整理的这篇文章主要介绍了
js+html5实现的自由落体运动效果代码，
前端之家小编觉得挺不错的，现在分享给大家，也给大家做个参考。
本文实例讲述了js+html5实现的自由落体运动效果。分享给大家供大家参考，具体如下：
运行效果截图如下：
具体代码如下：
canvas自由落体
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var canvasheight = 500;
var canvaswidth = 500;
var g = 9.8;
var plusV = 0.5;
function Block(vo,x,y,width,height,g,context) {
var _self = this;
_self.vo = vo || 0;
_self.x = x;
_self.y = y;
_self.prevX = x;
_self.prevY = y;
_self.g = g;
_self.height = height;
_self.width = width;
_self.prevTime = new Date().getTime();
context.fillStyle = "black";
_self.down = function () {
var time = (new Date().getTime() - _self.prevTime) / 200,y = _self.vo * time + 1 / 2 * _self.g * time * time + _self.y;
//console.log("down:time=" + time + ":y=" + y + ":" + _self.vo);
if (y + _self.height >= canvasheight) {
_self.g--;
_self.vo = _self.g * time;
_self.prevTime = new Date().getTime();
_self.up();
} else {
context.clearRect(_self.prevX,_self.prevY - 1,_self.prevX + _self.height,_self.prevY + _self.width);
context.fillRect(_self.x,_self.width,_self.height);
_self.prevX = x;
_self.prevY = y;
setTimeout(function () {
_self.down();
},30);
}
}
_self.up = function () {
var time = (new Date().getTime() - _self.prevTime) / 200,v = _self.vo - _self.g * time,y = canvasheight - _self.height - _self.vo * time + 1 / 2 * _self.g * time * time;
//console.log("up:time=" + time + ":v=" + v);
if (v <= 0) {
_self.vo = 0;
_self.y = y;
_self.prevTime = new Date().getTime();
if (y + _self.height < canvasheight) {
_self.down();
} else {
return;
}
} else {
context.clearRect(_self.prevX,_self.prevY + _self.width);
context.fillRect(x,_self.height);
_self.prevX = x;
_self.prevY = y;
setTimeout(function () {
_self.up();
},30);
}
}
}
window.onload = function () {
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
height = canvas.offsetHeight;
var block = new Block(0,100,20,context);
block.down();
}
