# How to use window.prompt()

> Learn how to use the browser window.prompt() API to get input from the user, including a default value, and how it returns null when they click Cancel.

Author: [Flavio Copes](https://flaviocopes.com/about/) | Published: 2021-04-07 | Topics: [JavaScript](https://flaviocopes.com/tags/js/) | Canonical: https://flaviocopes.com/javascript-prompt/

`prompt()` lets us get input from the user.

This API dates back to the dawn of the Web, and is supported by every browser.

It's very simple and I think it might come handy especially while prototyping an app, so you can just call a `prompt()` and be done with it, without setting up a form.

Here's how it works: you call `prompt()` 

You pass a string that represents the question we ask to the user:

```js
prompt("How old are you?")
```

This is how it looks in Chrome:

![Chrome browser prompt dialog with text How old are you, input field, Cancel and OK buttons](https://flaviocopes.com/images/javascript-prompt/chrome.png)


This is in Safari:

![Safari browser prompt dialog with text How old are you, input field, Cancel and OK buttons](https://flaviocopes.com/images/javascript-prompt/safari.png)

This is in Firefox:

![Firefox browser prompt dialog with text How old are you, input field, Cancel and OK buttons](https://flaviocopes.com/images/javascript-prompt/safari.png)

As you can see, it's different but the concept is the same

> You should call `window.prompt()`, but since `window` is implicit, `prompt()` works

The browser blocks the script execution until the user enters something and clicks any of the OK or Cancel button. You can't escape from that without clicking a button.

The value entered is then returned from this function, so we can assign it to a variable:

```js
const age = prompt("How old are you?")
```

You can pass a second parameter that's the default value prefilled in the prompt:

```js
const age = prompt("How old are you?", 18)
```

If the user enters nothing and clicks OK, an empty string will be returned.

If the user clicks the Cancel button, the `prompt()` function call returns `null`