revert pass dat

docs/v13/documentation/pass-data.md

@@ -1,25 +1,17 @@
 ---
 heading: Pass data from page to page
 ---
-When a user answers questions in your prototype, the kit stores their answers in session data. You can use or show their stored answers later.
 
-[View an example of what passing data looks like in a prototype](./examples/pass-data/vehicle-registration).
 
-To clear the data (for example at the end of a user research session) use the **Clear data** link in the footer.
+The kit stores data from all answers that users give in a prototype. This lets you use or show the answers later.
 
-> To take users from one page to another, your button must have a `form` tag. Do not add a `href` - this will turn the button into a link and means it will not submit any data.
+To clear the data (for example at the end of a user research session) use the **Clear data** link in the footer.
 
-Find out how to:
-- [show data in check your answers](./make-first-prototype/show-users-answers)
-- [set default data](set-data)
-- [show previous answers when a user goes back to a page](pass-answers) 
-- [use an answer to change the content on a page](conditional-content)
+[View an example of what passing data looks like in a prototype](./examples/pass-data/vehicle-registration).
 
 ## How to use
 
-The kit stores data from answers that users give in a prototype using the `name` attribute of the input. We can then use the `name` attribute to `call` this session data later on.
-
-Names cannot have spaces, so use hyphens and lowercase for simplicity.
+The kit stores data from answers that users give in a prototype using the `name` attribute of the input.
 
 For example, when a user enters their first name you could have this input:
 
@@ -37,34 +29,106 @@ You can show what the user entered later on like this:
 </p>
 ```
 
-## Checkboxes and radios 
+### Show answers in inputs
+
+If a user goes back to a page where they entered data, they would expect to see the answer they gave.
+
+Most inputs use the `value` option:
+
+```
+{{ govukInput({
+    name: 'first-name',
+    value: data['first-name']
+}) }}
+```
+
+For checkboxes the option is `values`, since more than one can be selected.
 
-To identify each radio or checkbox answer (like the country name) we use the `value` tag. For a text input, the `value` is whatever the user enters in the text area.
+### Show content if users have not answered optional questions
 
-For example, we’ve used `name: "country"` to set the list of countries:
+You can show content if data is currently blank using `or`, for example:
 
 ```
-{{ govukRadios({ 
-name: "country"
+{{ data['first-name'] or "First name not given" }}
 ```
 
-Then set each country as a `value`:
+You can also use this in a component. For example to show that a user has not answered an optional question on Check your answers:
 
 ```
-items: [
-{
-value: "england", 
-text: "England" 
-}, 
+{{ govukSummaryList({
+  rows: [
+    {
+      key: {
+        text: "First name"
+      },
+      value: {
+        text: data['first-name'] or "First name not given"
+      }
+    }
+  ]
+})}}
 ```
 
+
+### Set default data
+
+You can set default data in your prototype. This will appear without the user having to enter anything. 
+
+For example, if you want to test a journey where the user returns to review or update their information.
+
+If the user changes this data in the prototype, their new answers are saved.
+
+Add default data to your `app/data/session-data-defaults.js` file.
+
+For example, to set default data for the ‘First name’ and ‘Over 18’ inputs in the [passing data example](https://prototype-kit.service.gov.uk/docs/examples/pass-data/vehicle-registration) add:
+
+```
+module.exports = {
+
+  'first-name': 'Amina',
+  'over-18': 'yes'
+
+}
+```
+
+### Use links to set data
+
+You can use links to set data. If you want to test different scenarios, you can have links to set data for each scenario.
+
+To set data from a link, add a `?` to the `href` followed by the data you want to set:
+
+```
+<a href="/start?first-name=Amina">
+```
+
+To set more than one piece of data in a link, use an `&` between them:
+
+```
+<a href="/start?first-name=Amina&over-18=yes">
+```
+
+If the user changes this data in the prototype, their new answers will be saved.
+
+## Advanced features
+
 ### Checkboxes and radios using HTML
+
 If you are using the HTML components instead of Nunjucks, you need to use the `checked` function for radios and checkboxes. For example:
 
 ```
 <input class="govuk-checkboxes__input" id="waste-2" name="waste" type="checkbox" value="mines" {{ checked('waste','mines') }}>
 ```
 
+### Use the data on the server
+
+You can access the data on the server in a route function.
+
+For example for an input with `name="first-name"`:
+
+```
+var firstName = req.session.data['first-name']
+```
+
 ### Nested values
 
 For complex data you can use nested values, for example:
@@ -97,3 +161,15 @@ You can access the data on the server in a route function:
 ```
 var firstName = req.session.data['claimant']['first-name']
 ```
+
+### Ignore inputs
+
+To prevent an input being stored, use an underscore at the start of the name.
+
+```
+{{ govukInput({
+    name: '_secret'
+}) }}
+```
+
+To use this data you'll have to [write your own route](create-routes).