JavaScript中数组flat方法的使用与实现方法

let arr = [1,2,[3,[4,[5]]]]
const reasut = arr.flat()
console.log(reasut)
// [1, 2, 3, [4,[5]]]

let arr = [1,2,[3,[4,[5]]]]
const reasut2 = arr.flat(3)
console.log(reasut2)
// [1, 2, 3, 4, 5]

let arr = [1,2,[3,[4,[5]]]]
const reasut3 = arr.flat(Infinity)
console.log(reasut3)
// [1, 2, 3, 4, 5]

const arr2 = [1, , 2, [3]]
const reasut4 = arr2.flat()
console.log(reasut4)
// [1, 2, 3]

const arr5 = [1,2,[3,[4,5]], [6,[7]], 8]
function getFlatArr (list) {
  return list.reduce((pre, item) => {
    return pre.concat(item)
  }, [])
}
console.log(getFlatArr(arr5))
// [1,2,3,[4,5],6,[7],8]

const arr5 = [1,2,[3,[4,5]], [6,[7]], 8]

function getFlatArr (list) {
  let result = []
  list.forEach(element => {
    if (Array.isArray(element)) {
      result.push(...element)
    } else {
      result.push(element)
    }
  })
  return result
}
console.log(getFlatArr(arr5))
// [1,2,3,[4,5],6,[7],8]

const arr5 = [1,2,[3,[4,5]], [6,[7]], 8]
function getFlatArr (list) {
  return list.reduce((pre, item) => pre.concat(Array.isArray(item)? getFlatArr(item): item), [])
}
console.log(getFlatArr(arr5))
// [1, 2, 3, 4, 5, 6, 7, 8]

const arr5 = [1,2,[3,[4,5]], [6,[7]], 8]
function getFlatArr (list) {
  const result = []
  ;(function flat(list) {
    // forEach 自动去除数组空位
    list.forEach(item => {
      // 判断是不是数组
      if (Array.isArray(item)) {
        // 进行数组递归
        flat(item)
      } else {
        result.push(item)
      }
    })
  })(list)
  return result
}
console.log(getFlatArr(arr5))
// [1, 2, 3, 4, 5, 6, 7, 8]

const arr5 = [1,2,[3,[4,5]], [6,[7]], 8]
function getFlatArr (list) {
  const arrList = JSON.parse(jsON.stringify(list))
  const result = []
  while (arrList.length) {
    // 弹出堆栈中的数据
    let arr = arrList.shift()
    if (Array.isArray(arr)) arrList.unshift(...arr)
    else result.push(arr)
  }
  return result
}

console.log(getFlatArr(arr5))
// [1, 2, 3, 4, 5, 6, 7, 8]

const arr5 = [1,2,[3,[4,5]], [6,[7]], 8]
function getFlatArr (list, deepNum = 1) {
  return deepNum > 0? list.reduce((pre, item) => {
    return pre.concat(Array.isArray(item)? getFlatArr(item, deepNum - 1): item)
  }, []): list.slice()
}

console.log(getFlatArr(arr5))
// [1,2,3,[4,5], 6,[7], 8]

console.log(getFlatArr(arr5, 3))
// [1, 2, 3, 4, 5, 6, 7, 8]

const arr5 = [1,2,[3,[4,5]], [6,[7]], 8]
function getFlatArr (list, deepNum = 1) {
  const result = []
  ;(function flat(list, deepNum) {
    list.forEach(element => {
      // 判断当前元素是否为数组并控制递归的深度
      if (Array.isArray(element) && deepNum > 0) flat(element, deepNum - 1)
      else result.push(element)
    })
  })(list, deepNum)
  return result
}

console.log(getFlatArr(arr5))
// [1,2,3,[4,5], 6,[7], 8]

console.log(getFlatArr(arr5, 3))
// [1, 2, 3, 4, 5, 6, 7, 8]