Ext.apply VS Ext.applyIf

var source = new Array();

            source[0] = '1';
            source[1] = '2';
            source[2] = '3';


var destination = new Array();

            destination[0] = '4';
            destination[1] = '5';
            destination[2] = '6';
            destination[3] = '7';
            destination[4] = '8';
            destination[5] = '9';



// Ext.apply(obj1,obj2) copy all properties of obj2 to obj1 any way,replaceing
// the ones that obj1 has already defined

 Ext.apply(destination,source);
document.write(destination + '<br/>'); // 1,2,3,7,8,9

// Ext.applyIf(obj1,obj2) copy all properties of obj2 to obj1 only if
// they don't already exist

 Ext.applyIf(destination,source);
document.write(destination + '<br/>'); // 4,5,6,7,8,9