javascript - lodash takeRightWhile 从起始索引开始

Question

如何使用 lodash 的 takeRightWhile 和起始索引从数组中获取值？

这里的要点是，我想从特定的起点向后迭代，直到满足某个参数。

我想要做的示例:

const myArray = [
    {val: 'a', condition: true},
    {val: 'b', condition: false},
    {val: 'c', condition: true},
    {val: 'd', condition: true},
    {val: 'e', condition: true},
    {val: 'f', condition: true},
    {val: 'g', condition: false},
];
const startAt = 5;

const myValues = _.takeRightWhile(myArray, startAt, {return condition === true});
// --> [{val: 'c', condition: true}, {val: 'd', condition: true}, {val: 'e', condition: true}]

我查看了文档https://lodash.com/docs/4.17.4#takeRightWhile并且无法真正判断这是否可能。

是否有更好的方法来做到这一点？

Answer 1

洛达什的_.takeRightWhile()从末尾开始，到达谓词时停止。方法签名是:

_.takeRightWhile(array, [predicate=_.identity])

并且它不接受索引。

预测函数接收以下参数 - value , index , array 。 index是数组中当前项的位置。

要实现您的目标，请使用 _.take(startAt + 1)将数组切至(包括)起始索引，并使用 _.takeRightWhile() :

const myArray = [{"val":"a","condition":true},{"val":"b","condition":false},{"val":"c","condition":true},{"val":"d","condition":true},{"val":"e","condition":true},{"val":"f","condition":true},{"val":"g","condition":false}];

const startAt = 5;

const myValues = _(myArray)
  .take(startAt + 1) // take all elements including startAt
  .takeRightWhile(({ condition }) => condition) // take from the right 'till condition is false
  .value();

console.log(myValues);

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