typescript 具有空值和实际值的 lodash orderby 未正确排序

lodash orderby with null and real values not ordering correctly

提问by Ben Cameron

I have an Angular 2 typescript application that is using lodash for various things.

我有一个 Angular 2 打字稿应用程序，它使用 lodash 处理各种事情。

I have an array of objects that I am ordering using a property in the object...

我有一个对象数组，我使用对象中的属性进行排序...

_.orderBy(this.myArray, ['propertyName'], ['desc']);

This works well however my problem is that sometimes 'propertyName' can have a null value. These are ordered as the first item in a descending list, the highest real values then follow.

这很有效，但是我的问题是有时“propertyName”可以有一个空值。这些按降序排列为第一项，然后是最高的实际值。

I want to make these null values appear last in the descending ordering.

我想让这些空值按降序出现在最后。

I understand why the nulls come first.

我明白为什么空值首先出现。

Does anyone know how to approach this?

有谁知道如何解决这个问题？

采纳答案by Ben Cameron

The code I needed looks like this...

我需要的代码看起来像这样......

_.orderBy(this.myArray, [( o ) => { return o.myProperty || ''}], ['desc']); 

回答by Ori Drori

The _.orderBy()function's iteratees can use a method instead of a string. Check the value, and if it's nullreturn an empty string.

该_.orderBy()功能的iteratees可以使用，而不是一个字符串的方法。检查值，如果它null返回一个空字符串。

const myArray = [{ propertyName: 'cats' }, { propertyName: null }, { propertyName: 'dogs' }, { propertyName: 'rats' }, { propertyName: null }];

const result = _.orderBy(myArray, ({ propertyName }) => propertyName || '', ['desc']);

console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.2/lodash.min.js"></script>

The check can be simple (like the one I've used), which converts all falsy values to an empty string:

检查可以很简单（就像我使用过的那样），它将所有虚假值转换为空字符串：

propertyName || ''

If you need a stricter check, you can use the ternary operator, and handle just nullvalues:

如果您需要更严格的检查，您可以使用三元运算符，并仅处理null值：

propertyName === null ? '' : propertyName

---

---

Edit: Example with multiple ordering:

编辑：具有多个排序的示例：

const result = _.orderBy(myArray, (item) => [get(item, 'propertyName', 0), get(item, 'propertyName2')], ['desc', 'asc']);

This will order by propertyNamethen propertyName2.

这将在propertyName那时订购propertyName2。

If propertyNameis undefined/null then its default order will be set to 0. (and therefore will be displayed at last because of descordering on the propertyNamefield). In such case, propertyName2will therefore determine the ordering.

如果propertyName是 undefined/null 那么它的默认顺序将被设置为0。（因此将最终显示，因为desc在propertyName场上排序）。在这种情况下，propertyName2将因此确定排序。

回答by infinity

Just for future reference to others you can do this to sort ascending with falsey values at the end.

仅供将来参考其他人，您可以这样做以在最后对假值进行升序排序。

items =>
  orderBy(
    items,
    [
      i => !!i.attributeToCheck,
      i => {
        return i.attributeToCheck ? i.attributeToCheck.toLowerCase() : ''
      }
    ],
    ['desc', 'asc']
  )

回答by Stephen

This will put bad values at the bottom, and it differentiates between numbers and strings.

这会将错误的值放在底部，并区分数字和字符串。

const items = [] // some list

const goodValues = isAscending => ({ value }) => {
    if (typeof value !== 'string' && isNaN(value)) {
        return isAscending ? Infinity : -Infinity
    }

    return value || ''
}

const sortedItems = orderBy(
    items,
    [goodValues(isAscending), 'value'],
    [isAscending ? 'asc' : 'desc']
)

回答by lars1595

This worked for me

这对我有用

orders = [{id : "1", name : "test"}, {id : "1"}];
sortBy = ["id", "name"];
orderby(
            orders,
            sortBy.map(s => {
                return (r: any) => {
                    return r[s] ? r[s] : "";
                };
            })),
        );

回答by Johansrk

mine looks like this. PropName and sort are both variables in my solution

我的看起来像这样。PropName 和 sort 都是我的解决方案中的变量

return _.orderBy( myarray, [
  ( data ) => {
    if ( data[propName] === null ) {
        data[propName] = "";
    }
    return data[propName].toLowerCase();
    }
 ], [sort] );

I wanted tolowercase because otherwise the sorting is not correct if different casings

我想小写，否则如果不同的大小写排序不正确