Reputation: 62145

Okay to call prompt() this way?

Is it okay to call prompt this way:

  prompt('Enter your text here');

instead of:

  prompt('Enter your text here', '');

I.e. without passing a suggested input to it?

Upvotes: 3

Answers (5)

Gijs

Reputation: 5262

I thought the answer was 'yes', until I just saw that in IE7, this will result in having 'undefined' prefilled in the input box instead. Try it out for yourself in IE7 with a quick JSFiddle: http://jsfiddle.net/ALw6r/

Edit: from the comments, seems this is also broken in IE8.

Upvotes: 3

jsalonen

Reputation: 30481

Yes, it is OK.

The second parameter to prompt method is optional (see "window.prompt on MDN"). As according to ECMAScript specification (ECMA-262, section 4.3.9), a value of undefined is given to a variable which has no assigned value. In the prompt method, it doesn't matter whether you leave the second parameter as undefined or pass an empty string to it: both result in empty string as default value in the prompt.

In case you are wondering why this information is not available on DOM standards such as W3C DOM the answer is that it is a non-standard method that is "just" commonly supported by browsers (part of so called "DOM Level 0" spec). However, the upcoming HTML 5 is likely to define prompt (window.prompt) as a standard method (see "6.4 User prompts").

Upvotes: 6

T.J. Crowder

Reputation: 1074028

Yes, the second parameter is optional according to the HTML5 spec (the closest thing we currently have to a specification of prompt and alert and such):

The prompt(message, default) method, when invoked, must release the storage mutex, show the given message to the user, and ask the user to either respond with a string value or abort. The user agent must then pause as the method waits for the user's response. The second argument is optional. If the second argument (default) is present, then the response must be defaulted to the value given by default. If the user aborts, then the method must return null; otherwise, the method must return the string that the user responded with.

(My emphasis)

Upvotes: 3