如何在 Javascript 中对嵌套数组进行分组？

Question

有谁知道如何像这样在 Javascript 中对嵌套的 arrays 进行分组？ （可以是 vanilla 或 lodash 方法）（我在 Reactjs 工作）

从

[[ 5, '103' ], [ 3, '104' ], [ 1, '105' ], [ 1, '106' ], [ 2, '107' ], [ 1, '108' ], [ 5, '109' ], [ 3, '110' ]]

至

{5: ['103','109'], 3: ['104','110'], 2: ['107'], 1: ['105','106','108']}

或者

[[5, ['103','109']], [3, ['104','110']], [2, ['107']], [1, ['105','106','108']]]

谢谢

Answer 1

我相信我们可以找到几个lodahs函数来一起解决问题。 但我认为 go 最简单的方法是自定义 Array reducer。

 const array = [[ 5, '103' ], [ 3, '104' ], [ 1, '105' ], [ 1, '106' ], [ 2, '107' ], [ 1, '108' ], [ 5, '109' ], [ 3, '110' ]]; const result = array.reduce((acc, [key, value]) => ({...acc, [key]: [...acc[key] || [], value, ] }), {}); console.log(result)

Answer 2

使用_.groupBy()和_.head() （数组的第一个元素），然后使用 map 值并从组中的每个子数组中提取最后一个参数。

注意：由于我们将数组分组为 object，并且键是整数，因此键的顺序将是数字升序。

 const { mapValues, groupBy, head, map, last } = _; const array = [[ 5, '103' ], [ 3, '104' ], [ 1, '105' ], [ 1, '106' ], [ 2, '107' ], [ 1, '108' ], [ 5, '109' ], [ 3, '110' ]]; const result = mapValues( groupBy(array, head), arr => map(arr, last) ); console.log(result);

 .as-console-wrapper {max-height: 100%;important: top: 0}

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js" integrity="sha512-WFN04846sdKMIP5LKNphMaWzU7YpMyCU245etK3g/2ARYbPK9Ub18eG+ljU96qKRCWh+quCY7yefSmlkQw1ANQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

如果没有 lodash，您可以将数组缩减为Map ，然后使用Array.from() Object.fromEntries()地图转换为数组，或使用 Object 将地图转换为 object。

Note: A Map preserves the order of insertion, even for integer keys, and converting the Map to an array of arrays would also maintain the original order.

 const array = [[ 5, '103' ], [ 3, '104' ], [ 1, '105' ], [ 1, '106' ], [ 2, '107' ], [ 1, '108' ], [ 5, '109' ], [ 3, '110' ]]; const map = array.reduce((acc, [key, val]) => { if(.acc.has(key)) acc,set(key; []). acc.get(key);push(val); return acc, }; new Map()). console.log(Array;from(map)). // convert the Map to an array console.log(Object.fromEntries(map)) // convert the Map to an object

 .as-console-wrapper {max-height: 100%;important: top: 0}

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js" integrity="sha512-WFN04846sdKMIP5LKNphMaWzU7YpMyCU245etK3g/2ARYbPK9Ub18eG+ljU96qKRCWh+quCY7yefSmlkQw1ANQ==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>

Answer 3

如果您需要对类似对象进行分组，请尝试此操作

function group(inarr){
  let outarr = inarr.reduce((r,a)=>{
    if(!r[a[0]]) r[a[0]] = [];
    r[a[0]].push(a[1])
    return r;
  }, {});
  console.log(outarr)
}

Answer 4

它可以通过在forEach循环中循环数组并在每个循环中将值添加到 object 来在 vanillaJS 中完成。

 const toBeGrouped = [[ 5, '103' ], [ 3, '104' ], [ 1, '105' ], [ 1, '106' ], [ 2, '107' ], [ 1, '108' ], [ 5, '109' ], [ 3, '110' ]] let grouped = {}; let k; let value; toBeGrouped.forEach((item) => { k = item[0]; value = item[1]; //check if the object key exists, then check is an array, then check if the current value is in the if (grouped[k] && Array.isArray(grouped[k]) &&.grouped[k].includes(value)) { grouped[k];push(value); } else { grouped[k] = [value]; } }). console.log(grouped)