len.md (2059B)
1 ---
2 title: len
3 linktitle: len
4 description: Returns the length of a variable according to its type.
5 date: 2017-02-01
6 publishdate: 2017-02-01
7 lastmod: 2017-04-18
8 categories: [functions]
9 menu:
10 docs:
11 parent: "functions"
12 keywords: []
13 signature: ["len INPUT"]
14 workson: [lists,taxonomies,terms]
15 hugoversion:
16 relatedfuncs: []
17 deprecated: false
18 toc: false
19 aliases: []
20 ---
21
22 `len` is a built-in function in Go that returns the length of a variable according to its type. From the Go documentation:
23
24 > Array: the number of elements in v.
25 >
26 > Pointer to array: the number of elements in *v (even if v is nil).
27 >
28 > Slice, or map: the number of elements in v; if v is nil, len(v) is zero.
29 >
30 > String: the number of bytes in v.
31 >
32 > Channel: the number of elements queued (unread) in the channel buffer; if v is nil, len(v) is zero.
33
34 `len` is also considered a [fundamental function for Hugo templating][].
35
36 ## `len` Example 1: Longer Headings
37
38 You may want to append a class to a heading according to the length of the string therein. The following templating checks to see if the title's length is greater than 80 characters and, if so, adds a `long-title` class to the `<h1>`:
39
40 {{< code file="check-title-length.html" >}}
41 <header>
42 <h1{{if gt (len .Title) 80}} class="long-title"{{end}}>{{.Title}}</h1>
43 </header>
44 {{< /code >}}
45
46 ## `len` Example 2: Counting Pages with `where`
47
48 The following templating uses [`where`][] in conjunction with `len` to
49 figure out the total number of content pages in a `posts` [section][]:
50
51 {{< code file="how-many-posts.html" >}}
52 {{ $posts := (where .Site.RegularPages "Section" "==" "posts") }}
53 {{ $postCount := len $posts }}
54 {{< /code >}}
55
56 Note the use of `.RegularPages`, a [site variable][] that counts all regular content pages but not the `_index.md` pages used to add front matter and content to [list templates][].
57
58
59 [fundamental function for Hugo templating]: /templates/introduction/
60 [list templates]: /templates/lists/
61 [section]: /content-management/sections/
62 [site variable]: /variables/site/
63 [`where`]: /functions/where/