How to determine if there is a certain attribute in jquery

Jquery method to determine whether there is a certain attribute: 1. Determine through the "hasClass("new")" method; 2. Use the statement "if(typeof($("#aid").attr( "rel"))=="undefined")" to judge.

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JQuery determines whether a certain attribute exists hasAttr

In JQuery coding, we will judge whether an element has a certain attribute. For example, whether it contains the style of class="new". JQuery judgment is very simple because there is the hasClass method$ ("input[name=new]").hasClass("new") You can judge.

But sometimes we need to judge other attributes. For example, some a links contain the rel attribute, and some There is no rel attribute. How to judge at this time?

There is no ready-made method at this time. If there is an attribute $("#aid").attr("rel") will return rel value, if the rel attribute does not exist, "undefined"

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

Because the types are different.

It is recommended to use if(typeof($("#aid").attr("rel"))=="undefined") That’s it

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