code: func (c *Context) GetSupportedExtensions() []string {
  	ext := c.Call("getSupportedExtensions")
  	extensions := make([]string, ext.Length())
  	for i := 0; i < ext.Length(); i++ {
  		extensions[i] = ext.Index(i).String()
  	}
  	return extensions
  }
docs: // Returns a slice of supported extension strings.