使用Lodash/Underscore从对象列表中跳过并返回对象

Question

我需要执行类似于C#中编写的以下操作:

int[] items = { 1, 2, 3, 4, 5, 6, 7 };
var a = items.Skip(2).Take(3);

哪个返回3,4和5

同样,我需要从对象列表中跳过记录

$scope.myObject = [ { Editable: true, Name: "Daniel Test", Site: "SE100"},
                    { Editable: true, Name: "Test new", Site: "SE100"},
                    { Editable: false, Name: "Test", Site: "SE100"} ]

我需要跳过第一条记录并取回剩余的记录,即第1条记录

我怎么能用lodash/underscore做到这一点？

Answer 1

下划线的第一次和休息应该可以解决问题:

var a = _.first( _.rest(items, 2), 3);

和它自己的休息可以用来跳过第一条记录:

$scope.allButTheFirst = _.rest( $scope.myObject, 1)

可以使用链接使语句更加令人愉悦,从而提高透明度:

var a = _.chain(items)
    .rest(2)
    .first(3)
    .value();

由于使用lodash使用时@ RhysvanderWaerden的回答,指出drop代替first和take代替的rest.

Answer 2

在Lodash中,first和rest函数的行为与Underscore 不同.即他们不接受长度论证.相反drop,take应该使用:

const a = _.take(_.drop(items, skipCount), takeCount);

// or

const a = _(items).drop(skipCount).take(takeCount).value();

Answer 3

在lodash v3中你可以使用slice和take方法.作为替代,您可以使用数组方法切片

var offset = 2;
var limit = 3;
var items = [1, 2, 3, 4, 5, 6, 7];
var result1 = _(items).slice(offset).take(limit).value();
var result2 = items.slice(offset, offset + limit);

document.getElementById('result1').innerText = result1.toString();
document.getElementById('result2').innerText = result2.toString();

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/3.7.0/lodash.min.js"></script>
<pre>
  lodash v3: <span id="result1"></span>
  vanila JS: <span id="result2"></span>
</pre>

Answer 4

有这个

const skip = 0;
const take = 40;

您可以简单地做到这一点

return _.slice(items, skip, skip + take);

或仅使用本机js

items.slice(skip, skip + take);

Answer 5

/* PAGINATION WITH SORTING AND PAGING */
const page = 1;  // input page, min value 1
const limit = 2; // input limit min value 1

/* INPUT ARRAY */
const array = [
  { Editable: true,  Name: "Daniel Test", Site: "SE100"},
  { Editable: true,  Name: "Test new",    Site: "SE100"},
  { Editable: false, Name: "Test",        Site: "SE100"},
];

/* PAGINATION WITH SORTING AND PAGING */
const result = _(array)
                .orderBy(['Name'], ['asc']) // sort by ascendind
                .drop((page - 1) * limit)   // page in drop function starts from 0
                .take(limit)                // limit 2
                .value();

console.log(result);
console.log(JSON.stringify(result));
/*
  RESULT: 
  limit 2
  sort by ascendind
  [
     {
        "Editable":true,
        "Name":"Daniel Test", // name sorted by ascendind
        "Site":"SE100"
     },
     {
        "Editable":false,
        "Name":"Test",
        "Site":"SE100"
     }
  ]
*/

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.6/lodash.min.js"></script>