text: 
  /**
   * 实现字符串的反转
   * @param  str 字符串
   */
  function reverse(str){
  
  	var temp = "";
  	for(var i = str.length - 1; i >= 0; i--){
  		temp += str[i];
  	}
  	return temp
  }
  
  var rest = reverse("hello")
  console.log(rest)
  
  
  
  function reverse2(str){
  	var temp = "";
  	for(var i = str.length - 1; i >= 0; i--){
  		temp += str.charAt(i);
  	}
  	return temp
  }
  
  rest = reverse2('world')
  console.log(rest)