Necesito un código que me permita abrir ventanas y poder cerrarlas con un botón

Script
function closePopUp(){
    document.getElementById("popup").style.visibility = "hidden";

}

Java

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More than just a code generator. A tool that helps you with a wide range of tasks. All in one place.

Function from Description: Generate a function just by describing what is needs to do. Choose of many programming languages.
Text Description to SQL Command: Create a SQL command from a description.
Translate Languages: Translate code to any programming language.
Generate HTML from Description: Generate small HTML from Description.
Code to Explanation: Any code explained in plain english.
Fix invalid Code: To spot a missing character somewhere can be frustrating. This feature will help you to fix it.
Get Test for Code: This feature will help you to create tests for your code.
Class from Description: Generate a class just by describing what is needs to do. Choose of many programming languages.
Regex from Description: Create a regex from a description like "check for email".
Regex to Explanation: Create a plain english explanation from a regex.
Git Command from Description: Find the Git Command you are looking for from a description.
Linux Command: Get the linux command from a description.
Function from Docstring: Provide a docstring to generate the actual function.
Add typing to code: This feature will help you to add typing to your code.
Get Language from Code: Get the programming language from a code.
Time complexity: Get time complexity.
CSS from Description: Generate CSS from Description.
Meta Tags from Description: Generate Meta Tags from a Description.