text: /**
   * Created by 魏永戍 on 2017/1/24.
   */
  function main() {
      var canvas = document.getElementById('example');
      if (!canvas) {
          console.log('Failed to retrieve the <canvas> element');
          return;
      }
      
      var ctx = canvas.getContext('2d');
      
      ctx.fillStyle = 'rgb(0, 0, 255, 1.0)';
      ctx.fillRect(120, 10, 150, 150);
  }