title: Three.js Error creating WebGL context
body: <p>Friends, I need your help, the following code in three.js, all return null in this line:</p>
  
  <p>_context || _canvas.getContext( 'webgl', attributes ) || _canvas.getContext( 'experimental-webgl', attributes );</p>
  
  <hr>
  
  <pre><code>function initGL() {
  
      try {
  
          var attributes = {
              alpha: _alpha,
              depth: _depth,
              stencil: _stencil,
              antialias: _antialias,
              premultipliedAlpha: _premultipliedAlpha,
              preserveDrawingBuffer: _preserveDrawingBuffer
          };
  
          _gl = _context || _canvas.getContext( 'webgl', attributes ) || _canvas.getContext( 'experimental-webgl', attributes );
  
          if ( _gl === null ) {
  
              throw 'Error creating WebGL context.';
  
          }
  
      } catch ( error ) {
  
          console.error( error );
  
      }
  
      _glExtensionTextureFloat = _gl.getExtension( 'OES_texture_float' );
  </code></pre>
  
  <p>the attributes value:</p>
  
  <p><img src="https://i.stack.imgur.com/pk7Qs.png" alt="enter image description here"></p>
  
  <p>this is canvas:</p>
  
  <p><img src="https://i.stack.imgur.com/ivdtB.png" alt="enter image description here"></p>
  
  <p>Thanks a lot!</p>
  
  <p>~Rosone</p>