使用reduce实现map()

朱雀 2023-02-21 12:58 164阅读 0赞

#### 一、了解map()和reduce() [https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global\_Objects/Array/map][https_developer.mozilla.org_zh-CN_docs_Web_JavaScript_Reference_Global_Objects_Array_map] ####

map() 方法创建一个新数组，其结果是该数组中的每个元素是调用一次提供的函数后的返回值。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk3OTc4_size_16_color_FFFFFF_t_70]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk3OTc4_size_16_color_FFFFFF_t_70 1]  
（2）reduce（）  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk3OTc4_size_16_color_FFFFFF_t_70 2]

#### 二、具体实现 ####

Array.prototype.map = (func,callBackThis)=>{ 
    	return this.reduce(accu,currentValue,currentIndex,array)=>{ 
    		accu.push(func.call(callBackThis,currentValue,currentIndex,array))
    		return accu
    	},[])
    }

示例：![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk3OTc4_size_16_color_FFFFFF_t_70 3]  
可以 写的时候注意参数就好

[https_developer.mozilla.org_zh-CN_docs_Web_JavaScript_Reference_Global_Objects_Array_map]: https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Array/map
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[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk3OTc4_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20200630235539598.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk3OTc4,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk3OTc4_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20200701000534694.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODk3OTc4,size_16,color_FFFFFF,t_70
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