数组扁平化

简易一、使用扩展运算符实现一层扁平

---

function flat(array){
  return [].concat(...array);
}

const array = [1,[2,3,[4,5,6,[7,8,9,[10,11,12,13,14]]]]]
const result = flat(array);
console.log(result); // [ 1, 2, 3, [ 4, 5, 6, [ 7, 8, 9, [Array] ] ] ]

简易二、使用 reduce 与 concat 实现一层扁平

---

function flat(array){
    return array.reduce((accumulator,currentValue)=>{
        return accumulator.concat(currentValue)
    },[])
}

const array = [1,[2,3,[4,5,6,[7,8,9,[10,11,12,13,14]]]]]
const result = flat(array);
console.log(result); // [ 1, 2, 3, [ 4, 5, 6, [ 7, 8, 9, [Array] ] ] ]

方案一、使用数组API flat

const array = [1, [2, 3, [4, 5, 6, [7, 8, 9, [10, 11, 12, 13, 14]]]]];
const result = array.flat(2)
console.log(result);

方案二、使用 reduce + concat 递归实现深层扁平

---

完整写法

function flat(array, deep = 1) {
  if (deep > 0) {
    return array.reduce((accumulator, currentValue) => {
      if (!Array.isArray(currentValue)) {
        return accumulator.concat(currentValue);
      } else {
        return accumulator.concat(flat(currentValue, --deep));
      }
    }, []);
  } else {
    return array.slice();
  }
}

const array = [1, [2, 3, [4, 5, 6, [7, 8, 9, [10, 11, 12, 13, 14]]]]];
const result = flat(array, 2);
console.log(result); // 结果: [ 1, 2, 3, 4, 5, 6, [ 7, 8, 9, [ 10, 11, 12, 13, 14 ] ] ]

优雅简洁写法

function flat(array, deep = 1) {
  return deep > 0
    ? array.reduce(
        (accumulator, currentValue) =>
          accumulator.concat(
            Array.isArray(currentValue)
              ? flat(currentValue, --deep)
              : currentValue
          ),
        []
      )
    : array.slice();
}

const array = [1, [2, 3, [4, 5, 6, [7, 8, 9, [10, 11, 12, 13, 14]]]]];
const result = flat(array, 2);
console.log(result); // 结果: [ 1, 2, 3, 4, 5, 6, [ 7, 8, 9, [ 10, 11, 12, 13, 14 ] ] ]

方案三、使用 forEach + push 递归实现深层扁平

---

function flat(array, deep = 1) {
  const result = [];
  const recurse = function(currentArray,currentDeep){
    currentArray.forEach((currentValue)=>{
        if(Array.isArray(currentValue) && currentDeep>0){
            recurse(currentValue,--currentDeep)
        }else{
            result.push(currentValue)
        }
    })
  }
  recurse(array,deep);
  return result;
}

const array = [1, [2, 3, [4, 5, 6, [7, 8, 9, [10, 11, 12, 13, 14]]]]];
const result = flat(array, 2);
console.log(result); // 结果: [ 1, 2, 3, 4, 5, 6, [ 7, 8, 9, [ 10, 11, 12, 13, 14 ] ] ]

方案四、使用堆栈 循环迭代实现深层扁平

---

function flat(array) {
  const stack = [...array];
  const result = [];
  while (stack.length) {
    const currentValue = stack.shift();
    if (Array.isArray(currentValue)) {
      stack.unshift(...currentValue);
    } else {
      result.push(currentValue);
    }
  }
  return result;
}

const array = [1, [2, 3, [4, 5, 6, [7, 8, 9, [10, 11, 12, 13, 14]]]]];
const result = flat(array);
console.log(result); // 结果: [ 1,  2, 3,  4,  5,  6, 7,  8, 9, 10, 11, 12, 13, 14 ]

方案五、使用Generator循环迭代实现深层扁平

function* flat(array) {
  for (let item of array) {
    if (Array.isArray(item)) {
      yield* flat(item);
    } else {
      yield item;
    }
  }
}

const array = [1, [2, 3, [4, 5, 6, [7, 8, 9, [10, 11, 12, 13, 14]]]]];
const result = [...flat(array)];
console.log(result); // 结果: // 结果: [ 1,  2, 3,  4,  5,  6, 7,  8, 9, 10, 11, 12, 13, 14 ]