modeling-app/docs/kcl/assert.md

---
title: "assert"
excerpt: "Check a value at runtime, and raise an error if the argument provided"
layout: manual
---

Check a value at runtime, and raise an error if the argument provided

is false.

```js
assert(data: bool, message: string) -> ()
```

### Examples

```js
const myVar = true
assert(myVar, "should always be true")
```

![Rendered example of assert 0](data:image/png;base64,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

### Arguments

* `data`: `bool` (REQUIRED)
* `message`: `string` (REQUIRED)

### Returns

`()`