Event handlers in Javascript
JavaScript applications in browsers are largely event-driven. Events are actions that usually occur as a result of something the user does. For example, clicking a button is an event,as is changing a text field or moving the mouse over a link. For a script to react to an event, you define eventhandlers, such as onChange and onClick.
Event Applies to Occurs when Event handler Abort images User aborts the loading of an image (for example by clicking a link or clicking the Stopbutton) onAbort Blur windows and all form elements User removes input focus from window or form element onBlur Change text fields,textareas, select lists user changes value of element onChange Click buttons, radio buttons, checkboxes, submit buttons, reset buttons, links User clicks form element or link onClick DragDrop windows User drops an object onto the browser window, such as dropping a file on the browser window onDragDrop Error images, windows The loading of a document or image causes an error onError Focus windows and all form elements User gives input focus to window or form element onFocus KeyDown document, images, links text areas User depresses a key onKeyDown KeyPress documents, images, links, text areas User presses or holds down a key onKeyPress KeyUp documents,images, links, text areas User releases a key onKeyUp Load document body User loads the page in the browser onLoad MouseDown documents, buttons, links User depresses a mouse button onMouseDown MouseMove nothing by default User moves the cursor onMouseOut MouseOut areas, links User moves cursor out of a client-side image map or link onMouseOut MouseOver links User moves a cursor over a link onMouseOver MouseUp documents, buttons, links User releases a mouse button onMouseUp Move windows User or script moves a window onMove Reset forms User resets a form (clicks a reset button) onReset Resize windows User or script resizes a window onResize Select text fields, textareas User selects form elements input field onSelect Submit forms User submits a form onSubmit Unload document body User exits the page onUnload Example, of a script that calculates an expression and shows the value in a textfield
<HTML> <HEAD> <SCRIPT> <!-- start function calculate(f) { if (confirm("Are you sure?")) f.result.value = eval(f.expressie.value) else alert("Try again") } // end --> </SCRIPT> </HEAD> <BODY> <FORM> Type an expression: <INPUT type="text" name="expressie" size=15> <INPUT type="button" value="Calculate" onClick="calculate(this.form)"> <BR> Result: <INPUT type="text" name="result" size=15> </BODY> </HTML>If you want more info click here.
