1.淺拷貝

2.深拷貝

 1 function deepCopy(source){
 2   let target = {}
 3   for (const key in source) {
 4     const element = source[key];
 5     if(source.hasOwnProperty(key)){
 6       if (typeof element !== 'object') {
 
 7         target[key] = element
 8       } else {
 9         target[key] = deepCopy(element)
10       }
11     }
12   }
13   return target
14 }

陣列展平的方法：

1.先將陣列轉為string（此時已將陣列展開，逗號分隔），再用split轉為陣列

 1 let a = [1,2,3]
 2 console.info(a.toString()) // "1,2,3"
 3 a = [1, 2, [3, 4]]
 4 console.info(a.toString()) //
 
 "1,2,3,4"
 5 a = [1, 2, [3, 4, [5, 6], 7], 8]
 6 console.info(a.toString()) // "1,2,3,4,5,6,7,8"
 7 let b = a.toString().split(",") 
 8 console.info(b) // ["1", "2", "3", "4", "5", "6", "7", "8"]
 9 a = [1, 2, "a", [3, 4, [5, 'c', 6], 7], 8, {}, function(){}]
10 b = a.toString().split(",").map(item => Number.isNaN(Number(item)) ? item : Number(item))
 
11 console.info(b) // [ 1, 2, 'a', 3, 4, 5, 'c', 6, 7, 8 ]

以上只能對原始值有效，也算是一種思路。

2.ES6新增了 flat(n) -- 將巢狀陣列展開，n引數為展開層數，可用Infinity展開全部層級