refactor: 优化 canvas 实例 data 写法

pages/component/canvas/canvas.uvue

@@ -17,10 +17,10 @@
         <text id="testToDataURLResult">{{testToDataURLResult}}</text>
       </view>
 
-      <view class="text-group">
-        <text>测试 createImage 结果：</text>
-        <text id="testCreateImage">{{testCreateImage}}</text>
-      </view>
+      <view class="text-group">
+        <text>测试 createImage 结果：</text>
+        <text id="testCreateImage">{{testCreateImage}}</text>
+      </view>
 
       <!-- #ifdef WEB -->
       <button class="canvas-drawing-button" @click="canvasToBlob">canvasToBlob</button>
@@ -55,13 +55,14 @@
     context.scale(dpr, dpr);
   }
 
-  const API_PATH = ["arc", "arcTo", "bezierCurveTo", "quadraticCurve", "moveTo", "lineTo", "rect", "clip", "pattern"]
-  const API_DRAW = ["stroke", "strokeRect", "strokeText", "fill", "fillRect", "fillText", "drawImage", "drawImageLocal", "clearRect"]
-  const API_STATE = ["beginPath", "closePath", "reset", "transform", "rotate", "resetTransform", "save", "restore", "scale", "translate"]
-  const API_PROPERTIES = ["setLineCap", "setLineJoin", "setLineWidth", "setMiterLimit", "setFillStyle", "setStrokeStyle", "setGlobalAlpha", "setFontSize", "lineDash", "linearGradient", "radialGradient", "textAlign"]
 
   export default {
     data() {
+      const API_PATH = ["arc", "arcTo", "bezierCurveTo", "quadraticCurve", "moveTo", "lineTo", "rect", "clip", "pattern"]
+      const API_DRAW = ["stroke", "strokeRect", "strokeText", "fill", "fillRect", "fillText", "drawImage", "drawImageLocal", "clearRect"]
+      const API_STATE = ["beginPath", "closePath", "reset", "transform", "rotate", "resetTransform", "save", "restore", "scale", "translate"]
+      const API_PROPERTIES = ["setLineCap", "setLineJoin", "setLineWidth", "setMiterLimit", "setFillStyle", "setStrokeStyle", "setGlobalAlpha", "setFontSize", "lineDash", "linearGradient", "radialGradient", "textAlign"]
+
       return {
         title: 'Context2D',
         canvas: null as UniCanvasElement | null,