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Twitter{{#each(expression)}}
Deprecated 3.9
The as keyword signature, {{#each EXPRESSION as KEY}}FN{{else}}INVERSE{{/each}}, is deprecated in favor of Hash Expressions like {{#each(EXPRESSION, KEY=value)}}FN{{else}}INVERSE{{/each}}.
{{#each(EXPRESSION)}}FN{{else}}INVERSE{{/each}}
Render FN for each item in EXPRESSION’s return value. If EXPRESSION
is falsey or an empty list, render INVERSE.
{{#each(todos)}}
<li>{{name}}</li>
{{else}}
<li>No todos, rest easy!</li>
{{/each}}
Parameters
- EXPRESSION
{KeyLookup Expression|Call Expression}:An expression that typically returns a list like data structure.
If the value of the EXPRESSION is a can-define/list/list or can-list, the resulting HTML is updated when the list changes. When a change in the list happens, only the minimum amount of DOM element changes occur. The list itself can also change, and a diff will be performed, which also will perform a minimal set of updates. The special %key key is available within
FN.If the value of the key is an object,
FNwill be called for each property on the object. The special %key key is available withinFN. - FN
{sectionRenderer(context, helpers)}:A subsection that will be rendered with each item in
EXPRESSIONor property value inEXPRESSION. - INVERSE
{sectionRenderer(context, helpers)}:An optional subsection that will be rendered if
EXPRESSIONis falsey or an empty list or object.
{{#each(EXPRESSION, HASH_EXPRESSION)}}FN{{else}}INVERSE{{/each}}
Like a normal {{#each(EXPRESSION)}}, but uses Hash Expression to
add the current value, key, or index to the current scope.
{{#each(todos, todo=value num=index)}}
<li data-index="{{num}}">{{todo.name}}</li>
{{/each}}
Parameters
- EXPRESSION
{KeyLookup Expression|Call Expression}:An expression that returns a list or object like data structure.
- HASH_EXPRESSION
{Hash Expression}:A hash expression that aliases special properties for each iteration:
value: The current valuekey: The key of the current object itemindex: The index of the current array item
- FN
{sectionRenderer(context, helpers)}:A subsection that will be rendered with each item in
EXPRESSIONor property value inEXPRESSION. - INVERSE
{sectionRenderer(context, helpers)}:An optional subsection that will be rendered if
EXPRESSIONis falsey or an empty list or object.
{{#each(EXPRESSION)}}FN{{else}}INVERSE{{/each}}
Like a normal {{#each(EXPRESSION)}}, but adds each item in EXPRESSION as
KEY in FN’s can-view-scope.
{{#each(todos, todo=value)}}
<li>{{todo.name}}</li>
{{/each}}
Parameters
- EXPRESSION
{KeyLookup Expression|Call Expression}:An expression that returns a list or object like data structure.
- key
{key}:The name that:
- each item in
EXPRESSION’s list, or - each property value in
EXPRESSION’s object should take on inFN.
- each item in
- FN
{sectionRenderer(context, helpers)}:A subsection that will be rendered with each item in
EXPRESSIONor property value inEXPRESSION. - INVERSE
{sectionRenderer(context, helpers)}:An optional subsection that will be rendered if
EXPRESSIONis falsey or an empty list or object.
Use
Use the each helper to iterate over a array
of items and render the block between the helper and the slash.
For example, this template:
<ul>
{{#each(friends)}}
<li>{{name}}</li>
{{/each}}
</ul>
Rendered with:
{friends: [{name: "Austin"},{name: "Justin"}]}
Renders:
<ul>
<li>Austin</li>
<li>Justin</li>
</ul>
Object iteration
When iterating over can-map it will only iterate over the map’s keys and none of the hidden properties of a Map.
For example, this template:
<ul>
{{#each(person)}}
<li>{{.}}</li>
{{/each}}
</ul>
Rendered with:
{person: {name: 'Josh', age: 27}}
Renders:
<ul>
<li>Josh</li>
<li>27</li>
</ul>
Understanding when to use #each with lists
{{#each(key)}} iteration will do basic diffing and aim to only update the DOM where the change occurred. Whereas
{{#expression}} default iteration will re-render the entire section for any change in the list.
{{#expression}} iteration is the preferred method to use when a list is replaced or changing significantly.
When doing single list item changes frequently, {{#each(expression)}} iteration is the faster choice.
For example, assuming "list" is a can-define/list/list instance:
{{#each(list)}} and {{#list}} both iterate through an instance of can-define/list/list, however we setup the bindings differently.
{{#each(list)}} will setup bindings on every individual item being iterated through, while {{#list}} will not. This makes a difference in two scenarios:
You have a large list, with minimal updates planned after initial render. In this case,
{{#list}}might be more advantageous as there will be a faster initial render. However, if any part of the list changes, the entire{{#list}}area will be re-processed.You have a large list, with many updates planned after initial render. A grid with many columns of editable fields, for instance. In this case, you many want to use
{{#each(list)}}, even though it will be slower on initial render (we’re setting up more bindings), you’ll have faster updates as there are now many sections.