Edit in JSFiddle

var array1 = ['a', 'c','d','f','h'];
var array2 = ['a','b', 'c','d','e','f','g','h'];

document.write('array 1 : '+array1+'<br>');
document.write('array 2 : '+array2+'<br>');
//prototype method for array to find and remove matched element from argument array.
Array.prototype.diff = function(arr2) {
    this.sort();
    arr2.sort();
    for(var i = 0; i < this.length; i += 1) {
        if(arr2.indexOf( this[i] ) > -1){
            arr2.splice(arr2.indexOf( this[i] ), 1);
        }
    }
};

//code usage for above prototype method.
array1.diff(array2);

document.write('result array : '+array2);

//Note : I have used document.write() method to just show the out put in screen. But using document.write() is not recommended.