Using jquery to determine whether a property exists Hasattr solution _jquery

In the jquery code, we determine whether an element has an attribute, such as whether it contains a class= "new" style. jquery judgment is very simple, because there is hasclass this method $ ("input[name=new]"). Hasclass ("new") can be judged.

But sometimes we need to judge other attributes, such as a link that contains rel attributes, and some have no rel attribute.

Then there is no ready-made method. If there is a property $ ("#aid"). attr ("rel") returns the Rel value and returns "undefined" if no Rel property exists

Undefined is the undefined type, if ($ ("#aid"). attr ("rel") = = "undefined") this judgment may not be tenable.

Because the type is not the same.

It is recommended to use if (typeof ("#aid"). attr ("rel")) = = "undefined")