js怎么封装Canvas成插件

这次给大家带来js怎么封装Canvas成插件，js封装Canvas成插件的注意事项有哪些，下面就是实战案例，一起来看一下。

之前就说过，我想写一个canvas画统计图的插件，现在写好了

先说下实现的功能吧：

  1.可以通过自定义X轴坐标属性和Y轴坐标属性按比例画出统计图

  2.可以选择画折现图还是柱形统计图，或者两者都实现

  3.可以自由定义折现颜色，坐标颜色，柱形图颜色 和canvas边框颜色，当然边框你也可以选择要或者不要

  4.可以选择是否实现柱形图和折现图的动画实现

实现过程

画坐标——画箭头——做X轴和Y轴的标注——画柱形图——画折现图

话不多说，上代码

(function(window,document){
 var ChartDraws = function(options){
  if(!(this instanceof ChartDraws))return new ChartDraws(options);
  this.options = $.extend({
   //报表所需的参数
   "containerId" : "",  //canvas所在容器id
   "canvasWidth" : 400,
   "canvasHeight" : 300,
   "paddingLeft" : 20,
   "paddingTop" : 20,
   "columnChartData" :[], //柱形图的数量和对应得名称以及百分比
   "yChartData" :[],   //y轴的数量及名称
   "axisColor" : "white",  //坐标轴颜色
   "columnChartColor" : "#EEE685", //柱形图颜色
   "isNeedAnimation" : true, //是否需要动画
   "isNeedLineChart" : true, //是否需要折线图
   "isNeedColumnChart" : true, //是否需要柱形图
   "lineChartColor" : "#90EE90", //折线图颜色，当isNeedLineChart=true时有效
   "isNeedBorder" : false,  //canvas是否需要外边框
   "borderColor" : "white"  //外边框颜色
  },options);
  if(this.options.canvasWidth<=500)
  {
   this.axisBorderWidth = 3;
   this.fontSize = 8;
  }
  else if(this.options.canvasWidth<=800){
   this.axisBorderWidth = 4;
   this.fontSize = 12;
  }
  else{
   this.axisBorderWidth = 5;
   this.fontSize = 16;
  }
  var self = this;
  _init();
  function _init(){
   var canvasDom = document.createElement("canvas");
   canvasDom.id = self.options.containerId+"_"+"canvas";
   canvasDom.width = self.options.canvasWidth;
   canvasDom.height = self.options.canvasHeight;
   if(self.options.isNeedBorder){
    canvasDom.style.borderWidth = 1;
    canvasDom.style.borderStyle = "solid";
    canvasDom.style.borderColor = self.options.borderColor;
   }
   document.getElementById(self.options.containerId).appendChild(canvasDom);
   self.context = document.getElementById(self.options.containerId+"_"+"canvas");
   self.ctx = self.context.getContext("2d");
   _drawAxis();
  }
  function _drawAxis(){
   var XYData =transformAxis( [{x:self.options.paddingLeft,y:self.options.canvasHeight-self.options.paddingTop},{x:self.options.paddingLeft,y:self.options.paddingTop},{x:self.options.canvasWidth-self.options.paddingLeft,y:self.options.paddingTop}]);
   self.ctx.strokeStyle=self.options.axisColor;
   drawLine(self.ctx,XYData,self.axisBorderWidth);
   //画三角箭头
   //画y轴三角箭头
   drawLine(self.ctx,transformAxis([{x:self.options.paddingLeft-self.axisBorderWidth,y:self.options.canvasHeight-self.options.paddingTop-self.axisBorderWidth*2},{x:self.options.paddingLeft,y:self.options.canvasHeight-self.options.paddingTop},{x:self.options.paddingLeft+self.axisBorderWidth,y:self.options.canvasHeight-self.options.paddingTop-self.axisBorderWidth*2}]),self.axisBorderWidth);
   //画x轴三角箭头
   drawLine(self.ctx,transformAxis([{x:self.options.canvasWidth-self.options.paddingLeft-self.axisBorderWidth*2,y:self.options.paddingTop+self.axisBorderWidth},{x:self.options.canvasWidth-self.options.paddingLeft,y:self.options.paddingTop},{x:self.options.canvasWidth-self.options.paddingLeft-self.axisBorderWidth*2,y:self.options.paddingTop-self.axisBorderWidth}]),self.axisBorderWidth);
   _drawCoordinatePoints();
  }
  function _drawCoordinatePoints(){
   self.reactAngleWidth = (1-2*0.04)*(self.options.canvasWidth-(2*self.options.paddingLeft))/(self.options.columnChartData.length*2-1);
   self.lineDataList = [];
   for(var i = 0;i<self.options.columnChartData.length;i++)
   {
    drawXText(self.ctx,2*self.options.columnChartData[i].NO*self.reactAngleWidth+self.options.paddingLeft+0.04*(self.options.canvasWidth-(2*self.options.paddingLeft))+self.reactAngleWidth/2,self.options.paddingTop/2,self.options.columnChartData[i].Name);
    self.lineDataList.push({
     x:2*self.options.columnChartData[i].NO*self.reactAngleWidth+self.options.paddingLeft+0.04*(self.options.canvasWidth-(2*self.options.paddingLeft))+self.reactAngleWidth/2,
     y:self.options.canvasHeight-(self.options.paddingTop+(self.options.canvasHeight-2*self.options.paddingTop)*self.options.columnChartData[i].PT)
    })
   }
   //画Y轴title 画y轴虚线
   self.reactAngleHeight = (self.options.canvasHeight-2*self.options.paddingTop)/(self.options.yChartData.length+1);
   for(var j = 0;j<self.options.yChartData.length;j++)
   {
    drawYText(self.ctx,3*self.options.paddingLeft/4,self.options.paddingTop+self.reactAngleHeight*(j+1),self.options.yChartData[j].Name);
    //画虚线
    drawDottedLine(self.ctx,self.options.paddingLeft,self.options.paddingTop+self.reactAngleHeight*(j+1),self.options.canvasWidth-self.options.paddingLeft,self.options.paddingTop+self.reactAngleHeight*(j+1),self.options.canvasWidth-2*self.options.paddingLeft,10,self.axisBorderWidth/2);
   }
   _drawColumnChart();
  }
  function _drawColumnChart(){
   //柱形图循环
   var reactAngleTimer = 1;
   function loopColumnChart()
   {
    var columnChartLooped = window.requestAnimationFrame(loopColumnChart);
    if(reactAngleTimer<=100)
    {
     for(var k=0;k<self.options.columnChartData.length;k++)
     {
      self.ctx.fillStyle =self.options.columnChartColor;
      drawRectangle(self.ctx,self.lineDataList[k].x-self.reactAngleWidth/2,self.options.canvasHeight-((self.options.canvasHeight-2*self.options.paddingTop)*self.options.columnChartData[k].PT*reactAngleTimer/100+self.options.paddingTop),self.reactAngleWidth,(self.options.canvasHeight-2*self.options.paddingTop)*self.options.columnChartData[k].PT*reactAngleTimer/100);
     }
     reactAngleTimer++;
    }
    else
    {
     window.cancelAnimationFrame(columnChartLooped);
     columnChartLooped = null;
     reactAngleTimer = 1;
     if(self.options.isNeedLineChart)
     {
      loopLineChart();
     }
    }
   }
   //折线图循环
   var lineTimer = 0;
   function loopLineChart()
   {
    var lineChartLooped = window.requestAnimationFrame(loopLineChart);
    if(lineTimer<self.lineDataList.length-1)
    {
     self.ctx.lineWidth = 2*self.axisBorderWidth/3;
     if(lineTimer == 0)
     {
      drawCircle(self.ctx,self.lineDataList[lineTimer].x,self.lineDataList[lineTimer].y);
     }
     drawCircle(self.ctx,self.lineDataList[lineTimer+1].x,self.lineDataList[lineTimer+1].y);
     self.ctx.beginPath();
     self.ctx.moveTo(self.lineDataList[lineTimer].x,self.lineDataList[lineTimer].y);
     self.ctx.lineTo(self.lineDataList[lineTimer+1].x,self.lineDataList[lineTimer+1].y);
     self.ctx.strokeStyle = self.options.lineChartColor;
     self.ctx.lineWidth = 2*self.axisBorderWidth/3;
     self.ctx.stroke();
     lineTimer++;
    }
    else
    {
     window.cancelAnimationFrame(lineChartLooped);
     lineChartLooped = null;
     lineTimer = 0;
    }
   }
   //画柱形图
   function drawRectangle(context,x,y,width,height){
    context.beginPath();
    context.fillRect(x,y,width,height);
   }
   //画圆
   function drawCircle(context,x,y){
    context.beginPath();
    context.arc(x,y,self.axisBorderWidth/2,0,2*Math.PI,true);
    context.strokeStyle=self.options.lineChartColor;
    context.stroke();
    context.closePath();
   }
   if(self.options.isNeedAnimation)
   {
    if(self.options.isNeedColumnChart)
    {
     loopColumnChart();
    }
    else
    {
     if(self.options.isNeedLineChart) {
      loopLineChart();
     }
    }
   }
   else
   {
    if(self.options.isNeedColumnChart)
    {
     for(var k=0;k<self.options.columnChartData.length;k++)
     {
      self.ctx.fillStyle =self.options.columnChartColor;
      drawRectangle(self.ctx,self.lineDataList[k].x-self.reactAngleWidth/2,self.options.canvasHeight-((self.options.canvasHeight-2*self.options.paddingTop)*self.options.columnChartData[k].PT+self.options.paddingTop),self.reactAngleWidth,(self.options.canvasHeight-2*self.options.paddingTop)*self.options.columnChartData[k].PT);
     }
    }
    if(self.options.isNeedLineChart) {
     for (var l = 0; l < self.lineDataList.length - 1; l++) {
      self.ctx.lineWidth = 4;
      if (l == 0) {
       drawCircle(self.ctx, self.lineDataList[l].x, self.lineDataList[l].y);
      }
      drawCircle(self.ctx, self.lineDataList[l + 1].x, self.lineDataList[l + 1].y);
      self.ctx.beginPath();
      self.ctx.moveTo(self.lineDataList[l].x, self.lineDataList[l].y);
      self.ctx.lineTo(self.lineDataList[l + 1].x, self.lineDataList[l + 1].y);
      self.ctx.strokeStyle = self.options.lineChartColor;
      self.ctx.lineWidth = 2*self.axisBorderWidth/3;
      self.ctx.stroke();
     }
    }
   }
  }
  function transformAxis(data)
  {
   var newData=[];
   for(var i=0;i<data.length;i++){
    newData.push({
     x:data[i].x,
     y:self.options.canvasHeight-data[i].y
    })
   }
   return newData;
  }
  function drawLine(context,point,width){
   context.beginPath();
   context.moveTo(point[0].x,point[0].y);
   if(point.length>2)
   {
    for(var i=1;i<point.length;i++)
    {
     context.lineTo(point[i].x,point[i].y);
    }
   }
   context.lineWidth = width;
   context.lineJoin=&#39;round&#39;;
   context.stroke();
   context.closePath();
  }
  //画y轴title
  function drawYText(context,x,y,str) {
   context.beginPath();
   context.font = &#39;{fontSize} Microsoft Yahei&#39;.replace("{fontSize}",self.fontSize+"px");
   context.fillStyle = &#39;white&#39;;
   context.textAlign = &#39;right&#39;;
   context.fillText(str,x,self.options.canvasHeight-y);
   context.closePath();
  }
  //画x轴title
  function drawXText(context,x,y,str) {
   context.beginPath();
   context.font = &#39;{fontSize} Microsoft Yahei&#39;.replace("{fontSize}",self.fontSize+"px");
   context.fillStyle = &#39;white&#39;;
   context.textAlign = &#39;center&#39;;
   context.fillText(str,x,self.options.canvasHeight-y);
   context.closePath();
  }
  function drawDottedLine(context,x1,y1,x2,y2,totalLength,length,lineWidth){
   y1 = self.options.canvasHeight-y1;
   y2 = self.options.canvasHeight-y2;
   var dashLen = length === undefined ? 5 : length;
   //计算有多少个线段
   context.beginPath();
   var num = Math.floor(totalLength/dashLen);
   context.lineWidth = lineWidth;
   for(var i = 0 ; i < num; i++)
   {
    context[i%2==0 ? &#39;moveTo&#39; : &#39;lineTo&#39;](x1+(x2-x1)/num*i,y1+(y2-y1)/num*i);
   }
   context.stroke();
  }
 };
 window.ChartDraws = ChartDraws;
}(window,document));

下面还有一个是实现requestAnimationFrame浏览器兼容的

(function(){
 var lastTime = 0;
 var prefixes = ['ms','webkit','o','moz']; //各浏览器前缀
 var requestAnimationFrame = window.requestAnimationFrame;
 var cancelAnimationFrame = window.cancelAnimationFrame;
 var prefix;
 //通过遍历各浏览器前缀，来得到requestAnimationFrame和cancelAnimationFrame在当前浏览器的实现形式
 for( var i = 0; i < prefixes.length; i++ ) {
  if ( requestAnimationFrame && cancelAnimationFrame ) {
   break;
  }
  prefix = prefixes[i];
  requestAnimationFrame = requestAnimationFrame || window[ prefix + &#39;RequestAnimationFrame&#39; ];
  cancelAnimationFrame = cancelAnimationFrame || window[ prefix + &#39;CancelAnimationFrame&#39; ] || window[ prefix + &#39;CancelRequestAnimationFrame&#39; ];
 }
 //如果当前浏览器不支持requestAnimationFrame和cancelAnimationFrame，则会退到setTimeout
 if ( !requestAnimationFrame || !cancelAnimationFrame ) {
  requestAnimationFrame = function( callback, element ) {
   var currTime = new Date().getTime();
   //为了使setTimteout的尽可能的接近每秒60帧的效果
   var timeToCall = Math.max( 0, 16 - ( currTime - lastTime ) );
   var id = window.setTimeout( function() {
    callback( currTime + timeToCall );
   }, timeToCall );
   lastTime = currTime + timeToCall;
   return id;
  };
  cancelAnimationFrame = function( id ) {
   window.clearTimeout( id );
  };
 }
 window.requestAnimationFrame = requestAnimationFrame;
 window.cancelAnimationFrame = cancelAnimationFrame;
}());

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