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```js const json = { id: 1, children: [ { id: 2, children: [{ id: 3, children: [] }] }, { id: 4, children: [ { id: 5, children: []...

```js /** * dfs * @param {character[][]} grid * @return {number} */ var numIslands = function(grid) { let sum = 0; grid[-1] = []; grid[grid.length] = []; for(let i =...

```js var object = { 'a': [{ 'b': { 'c': 3 } }] }; console.log(_get(object, 'a[0].b.c')); // => 3 console.log(_get(object, ['a', '0', 'b', 'c'])); // => 3 console.log(_get(object, 'a.b.c', 'default'));...

解决循环引用，和拷贝不可枚举对象！！ ```js /** * 深拷贝会拷贝不可枚举属性，浅拷贝不会 * @param {*} target * @param {*} map 避免循环引用 */ function _deepClone(target, map = new Map()) { if(typeof target !== "object" || target === null)...

```js // Array.prototype.flat() 扁平化数组，参数代表展开的层数(默认1) const arr = [1,2,[3,[4]]]; arr.flat(Infinity) // [1,2,3,4] /** * 无副作用(不会改变原数组) * @param {*} depth */ Array.prototype._flat = function (depth = 1) { return this.reduce((acc, cur) =>...

O(n)复杂度实现 ```js function transform(arr) { arr.sort((a, b) => a.id - b.id); // 对原数组id值进行升序排序 const result = []; let hashMap = new Map(); for (let i = 0; i < arr.length;...