JavaScript - Pop Ups

There are three common pop-ups used in Javascript: alert, prompt, and confirm.

Alert
Declaring the window objects is optional (window.alert vs alert).

function ShowAlert()
{
    alert("Hello World");
}

Confirm Box
A confirm box is often used if you want the user to verify or accept something. When a confirm box pops up, the user will have to click either "OK" or "Cancel" to proceed. If the user clicks "OK", the box returns true. If the user clicks "Cancel", the box returns false.

https://www.w3schools.com/jsref/met_win_confirm.asp

function ShowConfirm()
{
    var results;
    if (confirm("PRESS A BUTTON") === true)
    { results = "You pressed OK!"; }
    else
    { results = "You pressed Cancel!"; }

    alert(results);
}

Prompt
A prompt box is often used if you want the user to input a value before entering a page. When a prompt box pops up, the user will have to click either "OK" or "Cancel" to proceed after entering an input value. If the user clicks "OK" the box returns the input value. If the user clicks "Cancel" the box returns null.

function ShowPrompt()
{
    var yourName = prompt("What is your name?", "enter name");
    if (yourName != null)
    {alert("Hello " + yourName + "! How are you today?"); }
}

Line Breaks - To display line breaks inside a popup box, use a back-slash followed by the character n such as \n.