本文實例講述了JS+canvas動態繪餅圖的方法。分享給大家供大家參考，具體如下：
運行效果圖如下：
完整代碼：
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>m.survivalescaperooms.com canvas餅狀圖</title></head><body><canvas id="canvas" width="800" height="600" style="border:1px solid red"></canvas></body><script> var colors = (function () { return ( "aliceblue,antiquewhite,aqua,aquamarine,azure,beige,bisque,black,blanchedalmond,blue," + "blueviolet,brown,burlywood,cadetblue,chartreuse,chocolate,coral,cornflowerblue,cornsilk," + "crimson,cyan,darkblue,darkcyan,darkgoldenrod,darkgray,darkgreen,darkgrey,darkkhaki,darkmagenta," + "darkolivegreen,darkorange,darkorchid,darkred,darksalmon,darkseagreen,darkslateblue,darkslategray," + "darkslategrey,darkturquoise,darkviolet,deeppink,deepskyblue,dimgray,dimgrey,dodgerblue,firebrick," + "floralwhite,forestgreen,fuchsia,gainsboro,ghostwhite,gold,goldenrod,gray,green,greenyellow,grey," + "honeydew,hotpink,indianred,indigo,ivory,khaki,lavender,lavenderblush,lawngreen,lemonchiffon," + "lightblue,lightcoral,lightcyan,lightgoldenrodyellow,lightgray,lightgreen,lightgrey,lightpink," + "lightsalmon,lightseagreen,lightskyblue,lightslategray,lightslategrey,lightsteelblue,lightyellow," + "lime,limegreen,linen,magenta,maroon,mediumaquamarine,mediumblue,mediumorchid,mediumpurple," + "mediumseagreen,mediumslateblue,mediumspringgreen,mediumturquoise,mediumvioletred,midnightblue," + "mintcream,mistyrose,moccasin,navajowhite,navy,oldlace,olive,olivedrab,orange,orangered,orchid," + "palegoldenrod,palegreen,paleturquoise,palevioletred,papayawhip,peachpuff,peru,pink,plum,powderblue," + "purple,rebeccapurple,red,rosybrown,royalblue,saddlebrown,salmon,sandybrown,seagreen,seashell,sienna," + "silver,skyblue,slateblue,slategray,slategrey,snow,springgreen,steelblue,tan,teal,thistle,transparent," + "tomato,turquoise,violet,wheat,white,whitesmoke,yellow,yellowgreen" ).split(','); })(); function Bing(obj) { this.start = 0; for(var key in obj){ this[key] = obj[key]; } this.init(); } Bing.prototype = { init: function () { this.handle(); this.render(this.data2); this.drawText(); }, /** * 渲染頁面 * @param obj * @param i */ render: function (obj) { //3、計算每一個扇形的起始弧度和結束弧度 this.data2.forEach(function (v, i) { var obj = {}; //第一個扇形的起始弧度：start 結束：start+第一個扇形占據的弧度差 obj.start = this.start; obj.end = this.start + v.radian; this.start += v.radian; //繪制扇形 this.ctx.beginPath(); this.ctx.moveTo(300, 300); this.ctx.arc(300, 300, 150, obj.start, obj.end); this.ctx.fillStyle = colors[i * 15]; this.ctx.fill(); }, this); }, /** * 處理數據 */ handle:function(){ var sum = 0; this.data.forEach(function (v) { sum += v; }); //2、計算每一個數據所占的比重 this.data2 = this.data.map(function (v) { var obj = {}; obj.number = v; obj.ratio = v / sum;//每個數據占據的比重 obj.radian = 2 * Math.PI * v / sum;//該扇形所占據的弧度 obj.start = this.start; obj.end = this.start + obj.radian; this.start = obj.end; return obj; },this); }, drawText:function(){ this.ctx.font = "30px 微軟雅黑"; this.ctx.fillStyle = 'red'; this.data2.forEach(function(obj){ //計算文字所在的弧度 r2 = obj.start + obj.radian/2; //就按相對于圓心文字偏移的位置 b = this.r*Math.cos(r2); h = this.r*Math.sin(r2); //文字的位置 var x2 = this.x + b; var y2 = this.y + h; this.ctx.fillText(obj.number,x2,y2); },this); } }; var canvas = document.querySelector('canvas'); var ctx = canvas.getContext('2d'); var data = [1, 3, 5, 7, 9]; var bing = new Bing({ ctx:ctx, x:300, y:300, r:150, data:data });</script></html>更多關于JavaScript相關內容感興趣的讀者可查看本站專題：《JavaScript+HTML5特效與技巧匯總》、《JavaScript動畫特效與技巧匯總》、《JavaScript圖形繪制技巧總結》、《JavaScript切換特效與技巧總結》、《JavaScript錯誤與調試技巧總結》、《JavaScript數據結構與算法技巧總結》及《JavaScript數學運算用法總結》
希望本文所述對大家JavaScript程序設計有所幫助。
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