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JavaScript: The Definitive Guide

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JavaScript Reference

Element.onchange() Handler


Element.onchange() Handler---invoked when a form element's value changes


Navigator 2.0, Internet Explorer 3.0




The onchange() event handler of a form element is invoked by the web browser when the user changes the value displayed by a form element. Such a change may be an edit to the text displayed in Text, Textarea, Password, or FileUpload elements, or the selection or deselection of an option in a Select element. Note that this event handler is only invoked when the user makes such a change--it is not invoked if a JavaScript program changes the value displayed by an element.

Also note that the onchange() handler is not invoked every time the user enters or deletes a character in a text-entry form element. onchange() is not intended for that type of character-by-character event handling. Instead, onchange() is invoked when the user's edit is complete. The user assumes that the edit is complete when keyboard focus is moved to some other element--for example, when the user clicks on the next element in the form.

The onchange() event handler is a function defined through the onchange attribute of the HTML tag that defined the form element. The value of this attribute is a string that may contain any number of JavaScript statements, separated by semicolons. In Navigator 3.0, the onchange() event handler may also be defined by assigning a function directly to the onchange property of a form element.

The onchange() event handler is not used by the Hidden element, or by any of the button elements. Those elements, Button, Checkbox, Radio, Reset, and Submit use the onclick() event handler instead.

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