JavaScript - multi-line textbox in prompt()?

Is there anyway to make the textbox/input box in prompt multiline?

Answers:

Answer

No, browsers only allow single-line input for prompt(). However, with a simple change to the jQuery Alert Dialogs library you could get multi-line input there. Take jquery.alerts.js, look for <input type="text" size="30" id="popup_prompt" /> and replace it by <textarea rows="5" cols="30" id="popup_prompt"></textarea>. That should do to have a multi-line input field show up when calling jPrompt().

Edit: As Mulletfingers999 points out in a comment, jQuery Alert Dialogs have been deprecated in favor of jQuery UI dialogs. There you can also show a "modal" dialog, that dialog can have arbitrary content however - meaning that a <textarea> tag is possible if you want multi-line input.

Answer

Use \n encased in double quotes ("\n")

prompt("This\nis\nmultiline");
Answer

For pretty much any user-facing web application these days, you're going to want to avoid using clunky old dialogs like alert() and prompt(). Almost any library you're using should have a much better answer. jquery would be fine as others have said. It would also be good to think of how you might eliminate a need for modality by designing a more clever interface.

"Interestingly", in Firefox they are already using XUL and reinventing a lot of user interface based on that (instead of relying on the "common dialogs" of the underlying OS). There's a template for modal dialogs in /source/toolkit/components/prompts/content/tabprompts.xml:

<vbox anonid="infoContainer" align="center" pack="center" flex="1">
    <description anonid="info.title" class="info.title" hidden="true" />
    <description anonid="info.body" class="info.body"/>
</vbox>

<row anonid="loginContainer" hidden="true" align="center">
    <label anonid="loginLabel" value="&editfield0.label;" control="loginTextbox"/>
    <textbox anonid="loginTextbox"/>
</row>

<row anonid="password1Container" hidden="true" align="center">
    <label anonid="password1Label" value="&editfield1.label;" control="password1Textbox"/>
    <textbox anonid="password1Textbox" type="password"/>
</row>

<row anonid="checkboxContainer" hidden="true">
    <spacer/>
    <checkbox anonid="checkbox"/>
</row>

What they do is just hide the elements of the UI that they don't need. In the case of a call to prompt, they re-use the user name field and keep the password and checkbox elements hidden. You can see this happening in /source/toolkit/components/prompts/src/CommonDialog.jsm#52:

case "prompt":
  this.numButtons = 2;
  this.iconClass  = ["question-icon"];
  this.soundID    = Ci.nsISound.EVENT_PROMPT_DIALOG_OPEN;
  this.initTextbox("login", this.args.value);
  // Clear the label, since this isn't really a username prompt.
  this.ui.loginLabel.setAttribute("value", "");
  break;

Since it's more or less HTML, the only question is what the non-standard tag <textbox> means for the user interface. The XUL controls documentation informs us that it's only a one-line entry, you would need <textarea> for more:

https://developer.mozilla.org/en/XUL_controls

I thought it would be "fun" to look at the implementation in Chromium on top of GTK too. After a bit of digging through the circuitous wrappers of WebKit, I did manage to find chromium/src/chrome/browser/ui/gtk/js_modal_dialog_gtk.cc, specifically this part:

// Adjust content area as needed.  Set up the prompt text entry or
// suppression check box.
if (ui::MessageBoxFlags::kIsJavascriptPrompt == dialog_->dialog_flags()) {
  GtkWidget* content_area =
      gtk_dialog_get_content_area(GTK_DIALOG(gtk_dialog_));
  GtkWidget* text_box = gtk_entry_new();
  gtk_entry_set_text(GTK_ENTRY(text_box),
      UTF16ToUTF8(dialog_->default_prompt_text()).c_str());
  gtk_box_pack_start(GTK_BOX(content_area), text_box, TRUE, TRUE, 0);
  g_object_set_data(G_OBJECT(gtk_dialog_), kPromptTextId, text_box);
  gtk_entry_set_activates_default(GTK_ENTRY(text_box), TRUE);
}

The text_box is created with gtk_entry_new() and the GTK documentation states that GtkEntry is "A single line text entry field". For multi-line entry you would have to use GtkTextView:

http://developer.gnome.org/gtk/2.24/GtkTextView.html

So there's your answer not just of "can you?" but the smoking guns of why you can't (in a couple of popular browser implementations.) Unless there's a way to override that XUL in Firefox with an extension of some kind, which there may well be! I'll leave it as an exercise for the reader. :P

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