feat: compact filter

docs/source/zh-cn/filters/compact.md

@@ -2,9 +2,9 @@
 title: compact
 ---
 
-Removes any `nil` values from an array.
+从数组里移除任何 `null` 和 `undefined` 值。
 
-For this example, assume `site.pages` is an array of content pages for a website, and some of these pages have an attribute called `category` that specifies their content category. If we `map` those categories to an array, some of the array items might be `nil` if any pages do not have a `category` attribute.
+假设 `site.pages` 是网页列表，有些网页包含 `category` 属性用来标明类别。如果把它们 `map` 到数组里，那么对于没有 `category` 属性的元素就会是 `undefined`。
 
 输入
 ```liquid
@@ -26,7 +26,7 @@ For this example, assume `site.pages` is an array of content pages for a website
 - technology
 ```
 
-By using `compact` when we create our `site_categories` array, we can remove all the `nil` values in the array.
+使用 `compact` 创建 `site_categories` 数组，可以移除所有 `null` 和 `undefined` 值。
 
 输入
 ```liquid

src/builtin/filters/array.ts

@@ -1,4 +1,4 @@
-import { isArray, last as arrayLast } from '../../util/underscore'
+import { isArray, isNil, last as arrayLast } from '../../util/underscore'
 import { toArray } from '../../util/collection'
 import { isTruthy } from '../../render/boolean'
 import { FilterImpl } from '../../template/filter/filter-impl'
@@ -24,6 +24,10 @@ export function map<T1, T2> (this: FilterImpl, arr: Scope[], property: string) {
   return toArray(arr).map(obj => this.context.getFromScope(obj, property.split('.')))
 }
 
+export function compact<T> (this: FilterImpl, arr: T[]) {
+  return toArray(arr).filter(x => !isNil(x))
+}
+
 export function concat<T1, T2> (v: T1[], arg: T2[] | T2): (T1 | T2)[] {
   return toArray(v).concat(arg)
 }

test/integration/builtin/filters/array.ts

@@ -50,6 +50,12 @@ describe('filters/array', function () {
       return test(tpl, { arr: [a, b, c] }, 'Alice Bob Carol')
     })
   })
+  describe('compact', () => {
+    it('should compact array', function () {
+      const posts = [{ category: 'foo' }, { category: 'bar' }, { foo: 'bar' }]
+      return test('{{posts | map: "category" | compact}}', { posts }, 'foo,bar')
+    })
+  })
   describe('reverse', function () {
     it('should support reverse', () => test(
       '{{ "Ground control to Major Tom." | split: "" | reverse | join: "" }}',