Javascript do something only once

[joe92]

I need to create a javascript function which will only do something once. For example, there is a text box with preset text in it. Onfocus wipes that content so that the user can type their own in. However, I need it to only wipe the content once so I need that onfocus to be disabled after the first time. Is there a way of doing this all in javascript?

 

Is there a way of changing the javascript function using javascript? So that onfocus I could have something at the end of the function which then changes the onfocus event to something else.

 

Cheers

Joe

[trq]

You can easily make a JavaScript function overwrite itself:

 

var foo = function() {
  alert('say foo');
  foo = function() {
    alert('never again say foo');
  }
}
foo();
foo();
foo();

 

The first time you call foo() it will display 'say foo', every other call after that will display 'never again say foo'.

[nogray]

If you remove the function or only allow it to work one time, you would need to create a function for each input field (which defeats the purpose of a function). You can do something like this instead (notice the title is the same as the default value)

<input type="text" value="Default Value" title="Default Value" onfocus="if (this.value == this.title) this.value = '';" onblur="if (this.value == '') this.value = this.title;" />

[joe92]

Thank you very much nogray, that worked a treat!