js 数组 map方法

https://www.cnblogs.com/xuan52rock/p/4460949.html

https://jingyan.baidu.com/article/91f5db1b7453471c7e05e341.html

https://www.cnblogs.com/xiao-yu/archive/2011/05/28/2060587.html

https://www.cnblogs.com/fanbi/p/7573947.html

http://www.runoob.com/jsref/jsref-map.html