数组

1.提取数组中元素某一属性的值并生成新的数组

eg:  let arr1 = [

{a: 1, b: 2},

{a: 11, b: 22}

];

let arr2 = arr1.map(a => a.a);

console.log(arr2); // [1, 11]

2.两个数组获取交集

eg:  let arr1 = [1, 2, 3]，arr2 = [2, 6, 0];

let intersection = arr1.filter(function (val) {

return arr2.indexOf(val) > -1;

})

console.log(intersection); //[2]