javascript:仅尝试将数组展平 [英] javascript: Trying to flatten array only one level
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问题描述
我正在尝试编写一个将数组展平的函数.我的部分功能正在运行,另一半需要帮助.
I am trying to write a function to flatten an array. I have part of the function working and I need help in the other half.
flatten: function(anyArray, singleLevel) {
if (singleLevel == true) {
flatArray = Array.prototype.concat.apply([], anyArray);
return flatArray;
}
flatArray = Array.prototype.concat.apply([], anyArray);
if (flatArray.length != anyArray.length) {
flatArray = someObject.array.flatten(flatArray);
}
return flatArray;
}
如果我键入
.flatten([[[1],[1,2,3,[4,5],4],[2,3]]], true);
我希望它仅展平一个级别:
I want it to flatten only one level:
[[1],[1,2,3,[4,5],4],[2,3]]
推荐答案
现代JavaScript允许我们使用多种技术轻松处理此问题
Modern JavaScript allows us to handle this very easily using a variety of techniques
使用Array.prototype.flat
-
const arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
const flatArr =
arr.flat(1) // 1 is default depth
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
使用Array.prototype.flatMap
-
const arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
const flatArr =
arr.flatMap(x => x)
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
在Array.prototype.concat
const arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
const flatArr =
[].concat(...arr)
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
JavaScript的旧版本(ECMAScript 5和更低版本)可以使用Function.prototype.apply
-
Older version of JavaScript (ECMAScript 5 and below) can use techniques like Function.prototype.apply
-
var arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
var flatArr =
Array.prototype.concat.apply([], arr)
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
使用Array.prototype.reduce
-
var arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
var flatArr =
arr.reduce((r, a) => r.concat(a), [])
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
使用原始的for
循环-
var arr =
[ [ 1 ], [ 2, 3, [ 4, 5, [ 6 ] ] ], [ 7, [ 8, 9 ] ] ]
var flatArr =
[]
for (var i = 0; i < arr.length; i = i + 1)
flatArr = flatArr.concat(arr[i])
console.log(JSON.stringify(arr))
console.log(JSON.stringify(flatArr))
// [[1],[2,3,[4,5,[6]]],[7,[8,9]]]
// [1,2,3,[4,5,[6]],7,[8,9]]
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