JS異步編程一：用Jscex畫圓
作者：當(dāng)耐特磚家
關(guān)注老趙的jscex很久了，jscex利用eval(str)的無(wú)限可能，從“$async” 到“async”，從不支持if else 等 到支持 if else等·，jscex正在不斷完善和優(yōu)化當(dāng)中。
一.簡(jiǎn)介
關(guān)注老趙的jscex很久了，jscex利用eval(str)的無(wú)限可能，從“$async” 到“async”，從不支持if else 等 到支持 if else等·，jscex正在不斷完善和優(yōu)化當(dāng)中。jscex完全可以投入生產(chǎn)環(huán)境了··
二.畫圓
在支持html5的瀏覽器中執(zhí)行下面代碼：
- >
- <html>
- <body>
- <canvas id="myCanvas" width="480" height="300" style="border:1px solid #c3c3c3;">
- Your browser does not support the canvas element.
- canvas>
- <script type="text/javascript">
- var c = document.getElementById("myCanvas");
- var ccxt = c.getContext("2d");
- var x = 150;
- var y = 150;
- var r = 100;
- cxt.moveTo(x - r, y);
- for (var i = x - r; i < x + r + 1; i++) {
- var tempY = Math.pow(r * r - (x - i) * (x - i), 1 / 2);
- cxt.lineTo(i, y + tempY);
- }
- cxt.moveTo(x - r, y);
- for (var i = x - r; i < x + r + 1; i++) {
- var tempY = Math.pow(r * r - (x - i) * (x - i), 1 / 2);
- cxt.lineTo(i, y - tempY);
- }
- cxt.stroke();
- script>
- body>
- html>
在Canvas里顯示如下：
但是，我們明明是在畫圓，怎么沒(méi)有看到畫圓的過(guò)程？javascript就是這樣，解釋完就畫完了，而不會(huì)呈現(xiàn)解釋的過(guò)程，這也是為什么javascript不用考慮多線程問(wèn)題，僅僅UI線程。那么怎么看到畫圓的過(guò)程？
jscex閃亮登場(chǎng)！
- >
- <html>
- <body>
- <canvas id="myCanvas" width="480" height="300" style="border:1px solid #c3c3c3;">
- Your browser does not support the canvas element.
- canvas>
- <script language="javascript" type="text/javascript" src="lib/uglifyjs-parser.js">script>
- <script language="javascript" type="text/javascript" src="src/jscex.js">script>
- <script language="javascript" type="text/javascript" src="src/jscex.builderBase.js">script>
- <script language="javascript" type="text/javascript" src="src/jscex.async.js">script>
- <script type="text/javascript">
- var c = document.getElementById("myCanvas");
- var ccxt = c.getContext("2d");
- var x = 150;
- var y = 150;
- var r = 100;
- var drawAsync = eval(Jscex.compile("async", function () {
- cxt.moveTo(x - r, y);
- for (var i = x - r; i < x + r + 1; i++) {
- $await(Jscex.Async.sleep(10));
- var tempY = Math.pow(r * r - (x - i) * (x - i), 1 / 2);
- cxt.lineTo(i, y + tempY);
- cxt.stroke();
- }
- cxt.moveTo(x - r, y);
- for (var i = x - r; i < x + r + 1; i++) {
- $await(Jscex.Async.sleep(10));
- var tempY = Math.pow(r * r - (x - i) * (x - i), 1 / 2);
- cxt.lineTo(i, y - tempY);
- cxt.stroke();
- }
- }));
- drawAsync().start();
- script>
- body>
- html>
這樣就可以目睹畫圓全過(guò)程！
原文鏈接：http://www.cnblogs.com/iamzhanglei/archive/2011/08/16/2140113.html
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責(zé)任編輯：張偉
來(lái)源：
當(dāng)耐特磚家的博客
