> For the complete documentation index, see [llms.txt](https://docs.aurelia.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.aurelia.io/developer-guides/error-messages/0088-to-0723/aur0704.md).

# AUR0704

Template compilation error: Invalid command "yyyy" for \<let>. Only to-view/bind supported.

### **Error message**

Template compilation error: Invalid command "{{0:.command}}" for `<let>`. Only to-view/bind supported.

### **Parameters**

1. `command`: The invalid binding command used (e.g., `one-time`, `two-way`, `trigger`).

### Error explanation

This error occurs when the template compiler finds an unsupported binding command on an attribute of a `<let>` element. The `<let>` element is designed for creating variables within a template scope, and it only supports `.bind` (for simple assignment or expression evaluation) or no command (which defaults to `.to-view` / one-way binding). Other commands like `.one-time`, `.two-way`, `.trigger`, `.capture`, etc., are not applicable to `<let>` elements.

### Common causes

* Using `.one-time`, `.from-view`, `.two-way`, `.trigger`, or `.capture` on an attribute of a `<let>` element.

### How to fix

* Remove the unsupported binding command from the `<let>` element's attribute.
* Use `.bind` if you need to evaluate an expression.
* Use no binding command for simple one-way binding (`.to-view`).

### Example of Incorrect Usage:

```html
<!-- Error: .two-way is not supported on <let> -->
<let my-var.two-way="someValue"></let>

<!-- Error: .trigger is not supported on <let> -->
<let click-handler.trigger="doSomething()"></let>

<!-- Error: .one-time is not supported on <let> -->
<let config.one-time="initialConfig"></let>
```

### Example of Correct Usage:

```html
<!-- Using .bind (or default .to-view) -->
<let my-var.bind="someExpression"></let>
<let another-var="someStaticValue"></let>
<let user-name.bind="user.profile.name"></let>
```


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