Add Scratch function page

content/functions/scratch.md

@@ -10,11 +10,57 @@ tags: [iteration]
 categories: [functions]
 toc: false
 draft: false
-aliases: [/extras/scratch/]
+aliases: [/extras/scratch/,/doc/scratch/]
 notesforauthors:
 ---
 
-## Example
+`Scratch` -- a "scratchpad" for your page-scoped variables. In most cases you can do well without `Scratch`, but there are some use cases that aren't solvable with Go's templates without `Scratch`'s help, due to scoping issues.
+
+`Scratch` is added to both `Page` and `Shortcode` -- with following methods:
+
+* `Set` and `Add` takes a `key` and the `value` to add.
+* `Get` returns the `value` for the `key` given.
+* `SetInMap` takes a `key`, `mapKey` and `value`
+* `GetSortedMapValues` returns array of values from `key` sorted by `mapKey`
+
+`Set` and `SetInMap` can store values of any type.
+
+For single values, `Add` accepts values that support Go's `+` operator. If the first `Add` for a key is an array or slice, the following adds will be appended to that list.
+
+The scope of the backing data is global for the given `Page` or `Shortcode`, and spans partial and shortcode includes.
+
+Note that `.Scratch` from a shortcode will return the shortcode's `Scratch`, which in most cases is what you want. If you want to store it in the page scroped Scratch, then use `.Page.Scratch`.
+
+## Sample usage
+
+The usage is best illustrated with some samples:
+
+```
+{{ $.Scratch.Add "a1" 12 }}
+{{ $.Scratch.Get "a1" }} {{/* => 12 */}}
+{{ $.Scratch.Add "a1" 1 }}
+{{ $.Scratch.Get "a1" }} // {{/* => 13 */}}
+
+{{ $.Scratch.Add "a2" "AB" }}
+{{ $.Scratch.Get "a2" }} {{/* => AB */}}
+{{ $.Scratch.Add "a2" "CD" }}
+{{ $.Scratch.Get "a2" }} {{/* => ABCD */}}
+
+{{ $.Scratch.Add "l1" (slice "A" "B") }}
+{{ $.Scratch.Get "l1" }} {{/* => [A B]  */}}
+{{ $.Scratch.Add "l1" (slice "C" "D") }}
+{{ $.Scratch.Get "l1" }} {{/* => [A B C D] */}}
+
+{{ $.Scratch.Set "v1" 123 }}
+{{ $.Scratch.Get "v1" }}  {{/* => 123 */}}
+
+{{ $.Scratch.SetInMap "a3" "b" "XX" }}
+{{ $.Scratch.SetInMap "a3" "a" "AA" }}
+{{ $.Scratch.SetInMap "a3" "c" "CC" }}
+{{ $.Scratch.SetInMap "a3" "b" "BB" }}
+{{ $.Scratch.GetSortedMapValues "a3" }} {{/* => []interface {}{"AA", "BB", "CC"} */}}
+```
+
+**Note:** The examples above uses the special `$` variable, which refers to the top-level node. This is the behavior you most likely want, and will help remove some confusion when using `Scratch` inside page range loops -- and you start inadvertently calling the wrong `Scratch`. But there may be use cases for `{{ .Scratch.Add "key" "some value" }}`.
 
-## Advanced Example
 

content/tutorials/_index.md

@@ -1,5 +1,5 @@
 ---
-title: Overview
+title: Tutorials
 linktitle: Overview
 description:
 date: 2017-02-01

content/variables-and-params/_index.md

@@ -1,5 +1,5 @@
 ---
-title: Overview
+title: Variables and Params
 linktitle: Overview
 description: Page-, file-, taxonomy-, and site-level variables and parameters available in templates.
 date: 2017-02-01