Using alert, prompt, and confirm

Use alert, confirm, and prompt message boxes to obtain input from your user. The boxes are methods of the interface window object. Because the window object is at the top of the object hierarchy, you do not actually have to use the full name (for example, "window.alert()") of any of these message boxes, but it is a good idea to do so, because it helps you remember to which object they belong.

Alert Message Box

The alert method has one argument, the string of text you want to display to the user. The string is not HTML. The message box provides an OK button so the user can close it and is modal, that is, the user must close the message box before continuing.

window.alert("Welcome! Press OK to continue.");

Confirm Message Box

The confirm message box lets you ask the user a "yes-or-no" question, and gives the user the option of clicking either an OK button or a Cancel button. The confirm method returns either true or false. This message box is also modal: the user must respond to it (click a button), and thereby close it, before proceeding.

var truthBeTold = window.confirm("Click OK to continue. Click Cancel to stop.");
if (truthBeTold) {
window.alert("Welcome to our Web page!");
}  else  window.alert("Bye for now!");

Prompt Message Box

The prompt message box provides a text field in which the user can type an answer in response to your prompt. This box has an OK button and a Cancel button. If you provide a second string argument, the prompt message box displays that second string in the text field, as the default response. Otherwise, the default text is "<undefined>".

Like the alert( ) and confirm( ) methods, prompt displays a modal message box. The user must close it before continuing.

var theResponse = window.prompt("Welcome?","Enter your name here.");