## Built-in Helpers

In the last section you learned how to write a helper.
A helper is usually a simple function that can be
used in any template.
Ember comes with a few helpers that can make developing your
templates a bit easier.
These helpers can allow you to be more dynamic in
passing data to another helper or component.

### Using a helper to get a property dynamically

The [`{{get}}`](https://www.emberjs.com/api/ember/release/classes/Ember.Templates.helpers/methods/get?anchor=get) helper makes it easy to dynamically send the value of a
variable to another helper or component.
This can be useful if you want
to output one of several values based on the result of a computed property.

```handlebars
{{get address part}}
```

if the `part` computed property returns "zip", this will display the result of
`this.address.zip`. If it returns "city", you get `this.address.city`.

### Nesting built-in helpers

In the last section it was discussed that helpers can be nested.
This can be combined with these sorts of dynamic helpers.
For example, the [`{{concat}}`](https://www.emberjs.com/api/ember/release/classes/Ember.Templates.helpers/methods/get?anchor=concat) helper makes it easy to dynamically send
a number of parameters to a component or helper as a single parameter in the
format of a concatenated string.

```handlebars
{{get "foo" (concat "item" index)}}
```

This will display the result of `this.foo.item1` when index is 1,
and `this.foo.item2` when index is 2, etc.

### Built-in block helpers
Now let's say your template is starting to get a bit cluttered and you now want to clean up the logic in your templates. This can be achieved with the `let` block helper. The [`{{let}}`](https://www.emberjs.com/api/ember/release/classes/Ember.Templates.helpers/methods/get?anchor=let) helper lets you create new bindings in your template.

Say your template now looks like this:

```handlebars
Welcome back {{concat (capitalize person.firstName) ' ' (capitalize person.lastName)}}

Account Details:
First Name: {{capitalize person.firstName}}
Last Name: {{capitalize person.lastName}}
```

As mentioned in the previous section we use the `concat` helper to render both `person.firstName` and `person.lastName` in one go. But we also want to make sure that the names are capitalized. It gets a bit repetitive to keep writing `capitalize` and honestly, we might just forget it at some point. Thankfully, we can use the `{{let}}` helper to fix this:

```handlebars
{{#let (capitalize person.firstName) (capitalize person.lastName)
  as |firstName lastName|
}}
  Welcome back {{concat firstName ' ' lastName}}

  Account Details:
  First Name: {{firstName}}
  Last Name: {{lastName}}
{{/let}}
```

Now, as long as your template is wrapped in the `let` helper you can access the capitalized first name and last name as `firstName` and `lastName` instead of `(capitalize person.firstName)`.