Question

因此，如果我想从数组项中删除嵌套，我绝对可以这样做：

var nestedArrs = [[1],[2],[3],[4],[5]];
var denestedArr = [].concat.apply([], nestedArrs);
console.log(denestedArr) //prints [1, 2, 3, 4, 5];

但是如果我需要倒退并添加嵌套呢？

var unnestedArr = [7, 8, 9, 10];
var nestedArr = [] ? // Say I want to add nesting to every other item in arr
console.log(nestedArr); //so I wanted it to print [[7], 8, [9], 10]
//& nested Arr needs to be based upon the starting unnestedArr.

Answer 1

var unnestedArr = [7, 8, 9, 10];

var nestedArr = unnestedArr.map(function(item, index) {
    return index % 2 === 0 ? [ item ] : item;
});

console.log(nestedArr);

Answer 2

与Andreas的answer类似，我建议使用function programming的.map方法。如果您不喜欢对“其他”决策标准进行“硬编码”，则可以进行"mask"。

const unnestedArr = [7, 8, 9, 10];

// Here we define which items should be nested
const isEven = x => x % 2 === 0;
const nestCriterion = (item, index) => isEven(index);
const shouldBeNested = unnestedArr.map(nestCriterion); // = [true, false, true, false];

// Next we perform the nesting to the items we identified above
const nestedArr = unnestedArr.map((item, index) => {
    return shouldBeNested[index] ? [ item ] : item;
});

// Alternatively, we could've just used "one big function" like this:
const nestedArr2 = unnestedArr.map((item, index) => {
    if (index % 2 === 0) {
         return [ item ];
    }
    else {
        return item;
    }
});

// If we wanted to modify the array in place (instead of creating a new one)
// we could've used .forEach instead of .map and modified (mutated)
// elements of interest (e.g. by wrapping them in an array)

console.log(unnestedArr, nestedArr, nestedArr2);

这是jsbin.com

上的实现

如何将嵌套添加到数组Javascript中的项目

2 个答案: