为什么在ajQuery.extend中添加方法就报错，没有这个方法？
ajQuery.extend({
merge:function(first,second){
var len = +second.length,
j = 0,
i = first.length;
for ( ; j < len; j++ ) {
first[ i++ ] = second[ j ];
}
first.length = i;
return first;
},
b:function(){
alert('111');
}
})
$.merge is not a function
