es6 map和箭头函数

var  value = arr.map(function (x) {return x * x});

const arr = [1,2,3,4];

const value = arr.map(x => x * x);

//value = {[[1,1],[2,4],[3,9],[4,16]]}

 

nationArr = [{'id':1,'name':'汉族'},...]

this.nationArr.find(n => n.name === '汉族').id = 1