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。

我想做的例子：

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}]

我查看过文档https://lodash.com/docs/4.17.4#takeRightWhile并且无法确定这是否可行。

是否有更好的方法可以做到这一点？

Answer 1

Lodash的_.takeRightWhile()从结尾开始，到达谓词时停止。方法签名是：

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

它并不接受索引。

预测功能会收到以下参数 - 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)将数组切割为最多（包括）起始索引，并使用_.takeRightWhile()：

＆＃13;

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);

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

＆＃13;

Answer 2

您可以将切片与lodash一起使用

＆＃13;

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.slice(0, startAt), e => e.condition == true);

console.log(myValues);

＆＃13;

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

＆＃13;

lodash takeRightWhile从开始索引

2 个答案: