You need to add parentheses:
alert("HELLO");
W3Schools
w3schools.com › js › js_popup.asp
JavaScript Popup Boxes
To display line breaks inside a popup box, use a back-slash followed by the character n. ... If you want to use W3Schools services as an educational institution, team or enterprise, send us an e-mail: sales@w3schools.com · If you want to report ...
TutorialsTeacher
tutorialsteacher.com › javascript › display-popup-message-in-javascript
JavaScript Message Boxes: alert(), confirm(), prompt()
For example, you want to take the user's confirmation before saving, updating or deleting data. ... The confirm() function displays a popup message to the user with two buttons, OK and Cancel.
Videos
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How to Create JavaScript Alert Box | Popup Alert - YouTube
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Build a Popup with JavaScript | 1-Minute Tutorial - YouTube
How To Make A Popup Using HTML, CSS And JavaScript ...
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How to do JavaScript Popups (alert, confirm, prompt examples) - ...
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Top answer 1 of 8
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You need to add parentheses:
alert("HELLO");
2 of 8
12
Unlike VBScript, JavaScript requires parentheses around function calls.
Therefore, you need to write alert("Hello!");
It's also preferable (but not required) to end every statement with a semicolon ;.
Finally, if you aren't already, you need to put it in a script block, like this:
<script type="text/javascript">
alert("Hello!");
</script>
You can put JavaScript inside a script tag in an HTML page, or you can make a standalone .js file and double-click on it (in Windows) to run it using WSH.
MDN Web Docs
developer.mozilla.org › en-US › docs › Web › API › Window › alert
Window: alert() method - Web APIs | MDN
window.alert() instructs the browser to display a dialog with an optional message, and to wait until the user dismisses the dialog.
freeCodeCamp
freecodecamp.org › news › how-to-build-a-javascript-alert-box-or-popup-window
How to Build a JavaScript Alert Box or Popup Window
January 25, 2020 - There are three different kinds of popup methods used in JavaScript: window.alert(), window.confirm() and window.prompt(). The alert method displays messages that don’t require the user to enter a response.
Medium
medium.com › @ladypenguin1991 › javascript-popup-boxes-1b26d0aa89dc
Javascript Popup Boxes. I believe I can comfortably say that… | by CynthiaHarris | Medium
April 16, 2023 - With that in mind, let’s take a look at three different kinds of Javascript popup boxes: alert(), confirm(), and prompt(). Alert() is a built in function that allows for the display of a simple dialog box.
Quackit
quackit.com › javascript › javascript_alert_box.cfm
JavaScript Alert Box
Therefore, if you place the code within the <head> tags, your alert box will popup before the HTML elements are displayed. On the other hand, if you call your alert() function within the <body> tags, users will be able to see any HTML elements that have been rendered prior to the alert box code.
BitDegree
bitdegree.org › learn › javascript-alert
How to Create JavaScript Alert Box or Other Javascript Popup
August 8, 2017 - You will learn the usage of these different popups and the ways they improve websites. ... There are three types of JavaScript popup windows: Alert, Confirm and Prompt.
Laserfiche Answers
answers.laserfiche.com › questions › 61437 › How-to-display-a-pop-up-warning-from-JavaScript
How to display a pop up warning from JavaScript? - Laserfiche Answers
August 19, 2014 - If you want a popup, use alert(). ... As written, your code inserts a warning message after a field with the ageLimit CSS class.
Selenium
selenium.dev › documentation › webdriver › interactions › alerts
JavaScript alerts, prompts and confirmations | Selenium
August 14, 2025 - from selenium import webdriver from selenium.webdriver.common.by import By from selenium.webdriver.support.ui import WebDriverWait global url url = "https://www.selenium.dev/documentation/webdriver/interactions/alerts/" def test_alert_popup(): driver = webdriver.Chrome() driver.get(url) element = driver.find_element(By.LINK_TEXT, "See an example alert") element.click() wait = WebDriverWait(driver, timeout=2) alert = wait.until(lambda d : d.switch_to.alert) text = alert.text alert.accept() assert text == "Sample alert" driver.quit() def test_confirm_popup(): driver = webdriver.Chrome() driver.g
Edureka
edureka.co › blog › javascript-alert
Alert() in JavaScript | How to Create an Alert Message Box | Edureka
February 25, 2025 - The alert() method in JavaScript displays an alert box. It displays a specified message along with an OK button and is generally used to make sure that the user gets the information.
GeeksforGeeks
geeksforgeeks.org › javascript › explain-popup-message-using-event
Explain Popup Message using Event - JavaScript
July 29, 2024 - When JS displays an inbox, the user will see a popup box with an input location and the "OK" or "Cancel" buttons to continue after entering the input value. Example: Below example is illustrating the use of Prompt Box: ... <!DOCTYPE html> <html> ...
W3Schools
w3schools.com › jsref › met_win_alert.asp
Window alert() Method
The alert() method displays an alert box with a message and an OK button.
Codingem
codingem.com › home › javascript popup boxes
JavaScript Popup Boxes - codingem.com
July 10, 2025 - The prompt box displays a modal with a message that asks a user to enter text input. To create a prompt box in JavaScript, use the built-in prompt() method. This method takes two arguments: The text to be displayed.
GeeksforGeeks
geeksforgeeks.org › javascript › what-are-the-types-of-popup-box-available-in-javascript
What are the types of Popup box available in JavaScript ? - GeeksforGeeks
August 5, 2025 - In JavaScript, there are three types of popup boxes: alert, confirm, and prompt. The alert() displays a simple message, the confirm() asks the user to accept or cancel, and the prompt() requests user input with an optional default value.
EDUCBA
educba.com › home › software development › software development tutorials › javascript tutorial › javascript message box
JavaScript Message Box | How Does Message Box Work in JavaScript?
April 1, 2023 - Prompt box is one of the JavaScript Message Box used as an interactive popup window where the user wants to enter input before actual getting access of webpage.
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Retool
community.retool.com › 💬 app building
Alert.open() in Javascript - 💬 App Building - Retool Forum
January 29, 2024 - Looking for a way to create this kind of dialog popup screen in Javascript: I have a JSquery that I need to run on page load (which I have accomplished), but I need to force it to run a "alert" popup with a clickable …
SweetAlert2
sweetalert2.github.io
SweetAlert2 - a beautiful, responsive, customizable and accessible (WAI-ARIA) replacement for JavaScript's popup boxes
SweetAlert2 - a beautiful, responsive, customizable and accessible (WAI-ARIA) replacement for JavaScript's popup boxes
Adobe
acrobatusers.com › tutorials › popup_windows_part1
The alert box: Part 1 of 5 on popup windows
Acrobat has several types of built-in Popup Windows (alert, response, and file open), as well as functions for creating custom dialogs. The Alert Box is by far the most used dialog because it performs the most common operations. It displays short text messages (errors, warnings, etc.) and asks yes/no questions. Try it out by running the following code in the JavaScript Console.
Mobiscroll
demo.mobiscroll.com › javascript › popup
Javascript Popup Examples | Mobiscroll
February 24, 2026 - Pop-over examples with customizable content, button configuration and behavior. For vanilla JS to use everywhere. Last update: Mar 17, 2026