JavaScript实现扯网动画效果的示例代码

这篇文章主要为大家详细介绍了如何利用JavaScript语言实现扯网动画效果,文中的示例代码讲解详细,对我们学习JS有一定的帮助,需要的可以参考一下

演示

技术栈

JavaScript prototype(原型对象): 所有的 JavaScript 对象都会从一个 prototype(原型对象)中继承属性和方法。Date 对象从 Date.prototype 继承。 Array 对象从 Array.prototype 继承。 Person 对象从 Person.prototype 继承。 所有 JavaScript 中的对象都是位于原型链顶端的 Object 的实例。

JavaScript 对象有一个指向一个原型对象的链。当试图访问一个对象的属性时,它不仅仅在该对象上搜寻,还会搜寻该对象的原型,以及该对象的原型的原型,依次层层向上搜索,直到找到一个名字匹配的属性或到达原型链的末尾。

Date 对象, Array 对象, 以及 Person 对象从 Object.prototype 继承。

添加属性和方法 有的时候我们想要在所有已经存在的对象添加新的属性或方法。

另外,有时候我们想要在对象的构造函数中添加属性或方法。例如:

function Person(first, last, age, eyecolor) { this.firstName = first; this.lastName = last; this.age = age; this.eyeColor = eyecolor; } Person.prototype.nationality = "English"; 

也可以这样:

function Person(first, last, age, eyecolor) { this.firstName = first; this.lastName = last; this.age = age; this.eyeColor = eyecolor; } Person.prototype.name = function() { return this.firstName + " " + this.lastName; }; 

源码

css控制

* { margin: 0; overflow: hidden; -webkit-user-select: none; -moz-user-select: none; -ms-user-select: none; -o-user-select: none; user-select: none; } body { background: #F2F2F2; } #c { display: block; margin: 20px auto 0; } #info { position: absolute; left: -1px; top: -1px; width: auto; max-width: 420px; height: auto; background: #f2f2f2; border-bottom-right-radius: 10px; border:1px solid #333; } #top { background: #fff; width: 100%; height: auto; position: relative; border-bottom: 1px solid #eee; } p { font-family: Arial, sans-serif; color: #666; text-align: justify; font-size: 16px; margin: 10px 16px; } #github { color:#3377ee; font-family: Helvetica, Arial, sans-serif; font-size: 19px; display: block; margin: 0 auto; text-align: center; text-decoration:none; } #net { text-align:center; white-space:nowrap; font-size:19px; background:rgba(0,0,0,0.1); padding:8px 12px; border-radius:8px; display:block; color:#888; } #net > span { color:#3377ee; font-family: Helvetica, Arial, sans-serif; font-size: 14px; display: block; margin: 0 auto; text-align: center; text-decoration:none; } a { font-family: sans-serif; color: #444; text-decoration: none; font-size: 20px; } #site { float: left; margin: 10px; color: #ff9900; border-bottom: 1px dashed #ccc; padding-bottom:3px } #site:hover { color: #ffaa11; } #close { float: right; margin: 10px; } #p { font-family: Verdana, sans-serif; position: absolute; right: 10px; bottom: 10px; color: #4099ff; border: 1px dashed #4099ff; padding: 4px 8px; } #irc { display: block; text-align: center; margin-top:4px; color: #333; } #irc a { color: #3377ee; font-size: 17px } #irc-info { display: block; text-align: center; font-size: 14px; margin-top: -10px; color: #828282; margin-bottom:4px } #new { width: 100%; text-align: center; font-size: 18px; font-family: Helvetica; } #new a { font-size: 18px; color: #4099ff; } 

js部分

document.getElementById('close').onmousedown = function(e) { e.preventDefault(); document.getElementById('info').style.display = 'none'; return false; }; // settings var physics_accuracy  = 3, mouse_influence   = 20, mouse_cut         = 5, gravity           = 1200, cloth_height      = 30, cloth_width       = 50, start_y           = 20, spacing           = 7, tear_distance     = 60; window.requestAnimFrame = window.requestAnimationFrame || window.webkitRequestAnimationFrame || window.mozRequestAnimationFrame || window.oRequestAnimationFrame || window.msRequestAnimationFrame || function (callback) { window.setTimeout(callback, 1000 / 60); }; var canvas, ctx, cloth, boundsx, boundsy, mouse = { down: false, button: 1, x: 0, y: 0, px: 0, py: 0 }; var Point = function (x, y) { this.x      = x; this.y      = y; this.px     = x; this.py     = y; this.vx     = 0; this.vy     = 0; this.pin_x  = null; this.pin_y  = null; this.constraints = []; }; Point.prototype.update = function (delta) { if (mouse.down) { var diff_x = this.x - mouse.x, diff_y = this.y - mouse.y, dist = Math.sqrt(diff_x * diff_x + diff_y * diff_y); if (mouse.button == 1) { if (dist  boundsx ? this.x = 2 * boundsx - this.x : 1 > this.x && (this.x = 2 - this.x); this.y <1 ? this.y - :> boundsy && (this.y = 2 * boundsy - this.y); }; Point.prototype.attach = function (point) { this.constraints.push( new Constraint(this, point) ); }; Point.prototype.remove_constraint = function (constraint) { this.constraints.splice(this.constraints.indexOf(constraint), 1); }; Point.prototype.add_force = function (x, y) { this.vx += x; this.vy += y; }; Point.prototype.pin = function (pinx, piny) { this.pin_x = pinx; this.pin_y = piny; }; var Constraint = function (p1, p2) { this.p1     = p1; this.p2     = p2; this.length = spacing; }; Constraint.prototype.resolve = function () { var diff_x  = this.p1.x - this.p2.x, diff_y  = this.p1.y - this.p2.y, dist    = Math.sqrt(diff_x * diff_x + diff_y * diff_y), diff    = (this.length - dist) / dist; if (dist > tear_distance) this.p1.remove_constraint(this); var px = diff_x * diff * 0.5; var py = diff_y * diff * 0.5; this.p1.x += px; this.p1.y += py; this.p2.x -= px; this.p2.y -= py; }; Constraint.prototype.draw = function () { ctx.moveTo(this.p1.x, this.p1.y); ctx.lineTo(this.p2.x, this.p2.y); }; var Cloth = function () { this.points = []; var start_x = canvas.width / 2 - cloth_width * spacing / 2; for (var y = 0; y <= cloth_height; y++) { for (var x = 0; x <= cloth_width; x++) { var p = new Point(start_x + x * spacing, start_y + y * spacing); x != 0 && p.attach(this.points[this.points.length - 1]); y == 0 && p.pin(p.x, p.y); y != 0 && p.attach(this.points[x + (y - 1) * (cloth_width + 1)]) this.points.push(p); } } }; Cloth.prototype.update = function () { var i = physics_accuracy; while (i--) { var p = this.points.length; while (p--) this.points[p].resolve_constraints(); } i = this.points.length; while (i--) this.points[i].update(.016); }; Cloth.prototype.draw = function () { ctx.beginPath(); var i = cloth.points.length; while (i--) cloth.points[i].draw(); ctx.stroke(); }; function update() { ctx.clearRect(0, 0, canvas.width, canvas.height); cloth.update(); cloth.draw(); requestAnimFrame(update); } function start() { canvas.onmousedown = function (e) { mouse.button  = e.which; mouse.px      = mouse.x; mouse.py      = mouse.y; var rect      = canvas.getBoundingClientRect(); mouse.x       = e.clientX - rect.left, mouse.y       = e.clientY - rect.top, mouse.down    = true; e.preventDefault(); }; canvas.onmouseup = function (e) { mouse.down = false; e.preventDefault(); }; canvas.onmousemove = function (e) { mouse.px  = mouse.x; mouse.py  = mouse.y; var rect  = canvas.getBoundingClientRect(); mouse.x   = e.clientX - rect.left, mouse.y   = e.clientY - rect.top, e.preventDefault(); }; canvas.oncontextmenu = function (e) { e.preventDefault(); }; boundsx = canvas.width - 1; boundsy = canvas.height - 1; ctx.strokeStyle = '#888'; cloth = new Cloth(); update(); } window.onload = function () { canvas  = document.getElementById('c'); ctx     = canvas.getContext('2d'); canvas.width  = 560; canvas.height = 350; start(); };

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