// 201004291250 - Mootools clear input on focus, return default value if no data entered
// FROM:  Clear text field with mootools on focus. - MooTools Users | Google Groups http://bit.ly/cHPev3

/* 
	I've got this snippet that will clear the value on focus and if the value of 
	the focus is '' it will put the default value again in the input. You will 
	need the default value to be on an attribute of the input, like alt or 
	anyother (if you don't bother about validation). 
	
	Fábio Miranda Costa 
	Engenheiro de Computação 
	http://meiocodigo.com 

*/

// FUNCTION: 

Element.implement({ 
    clearFocusResetBlur: function(attr){ 
        var valueString = this.get(attr); 
        this.addEvents({ 
            'focus': function(){ 
                if( this.get('value') == valueString ) this.set('value',''); 
            }, 
            'blur': function(){ 
                if( this.get('value') == "" ) this.set('value',valueString); 
            } 
        }); 
    } 
}); 


// Usage
// HTML: 
// <input id="input_id" value="some value" alt="default value" /> 


// JS: 
$('.jform form .cleardefault').set('alt','value').clearFocusResetBlur('alt');

MOOTOOLS JS - Clear input field onClick onFocus on click focus active

form, javascript, js, textmate, function

JavaScript