/**
* flatten an array first level
* @method flatten
* @param array {Array}
* @return {Array} flatten array
*/
function flatten(array) {
  return array.reduce((acc, current) => acc.concat(current), []);
}


/**
* flatten an array recursively
* @method flattenDeep
* @param array {Array}
* @return {Array} flatten array
*/
function flattenDeep(array) {
  return array.reduce((acc, current) => {
    return Array.isArray(current) ? acc.concat(flattenDeep(current)) : acc.concat([current]);
  }, []);
}

/**
* flatten an array recursively limited by depth
* @method flattenDepth
* @param array {Array}
* @return {Array} flatten array
*/
function flattenDepth(array, depth) {
  if (depth === 0) {
    return array;
  }
  return array.reduce((acc, current) => {
    return Array.isArray(current) ? acc.concat(flattenDepth(current, --depth)) : acc.concat([current]);
  }, []);
}

这是递归方法。。。

function flatten(arr){
    let newArray = [];
    for(let i=0; i< arr.length; i++){
        if(Array.isArray(arr[i])){
          newArray =  newArray.concat(flatten(arr[i]))
        }else{
          newArray.push(arr[i])
        }
    }
  return newArray; 
}

console.log(flatten([1, 2, 3, [4, 5] ])); // [1, 2, 3, 4, 5]
console.log(flatten([[[[1], [[[2]]], [[[[[[[3]]]]]]]]]]))  // [1,2,3]
console.log(flatten([[1],[2],[3]])) // [1,2,3]

由于ES2019引入了flat和flatMap，因此任何阵列都可以这样做：

const myArr = [["$6"], ["$12"], ["$25"], ["$25"], ["$18"], ["$22"], ["$10"]]
const myArrFlat= myArr.flat(Infinity);
console.log(myArrFlat); // ["$6", "$12", "$25", ...]

裁判。https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat

我写的简单的flatten util

const flatten = (arr, result = []) => {
    if (!Array.isArray(arr)){
        return [...result, arr];
    }
     arr.forEach((a) => {
         result = flatten(a, result)
    })

    return result
}

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

最好使用javascript reduce函数。

var arrays = [["$6"], ["$12"], ["$25"], ["$25"], ["$18"], ["$22"], ["$10"], ["$0"], ["$15"],["$3"], ["$75"], ["$5"], ["$100"], ["$7"], ["$3"], ["$75"], ["$5"]];

arrays = arrays.reduce(function(a, b){
     return a.concat(b);
}, []);

或者，使用ES2015：

arrays = arrays.reduce((a, b) => a.concat(b), []);

js小提琴

Mozilla文档

以下代码将压平深度嵌套的数组：

/**
 * [Function to flatten deeply nested array]
 * @param  {[type]} arr          [The array to be flattened]
 * @param  {[type]} flattenedArr [The flattened array]
 * @return {[type]}              [The flattened array]
 */
function flattenDeepArray(arr, flattenedArr) {
  let length = arr.length;

  for(let i = 0; i < length; i++) {
    if(Array.isArray(arr[i])) {
      flattenDeepArray(arr[i], flattenedArr);
    } else {
      flattenedArr.push(arr[i]);
    }
  }

  return flattenedArr;
}

let arr = [1, 2, [3, 4, 5], [6, 7]];

console.log(arr, '=>', flattenDeepArray(arr, [])); // [ 1, 2, [ 3, 4, 5 ], [ 6, 7 ] ] '=>' [ 1, 2, 3, 4, 5, 6, 7 ]

arr = [1, 2, [3, 4], [5, 6, [7, 8, [9, 10]]]];

console.log(arr, '=>', flattenDeepArray(arr, [])); // [ 1, 2, [ 3, 4 ], [ 5, 6, [ 7, 8, [Object] ] ] ] '=>' [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]