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This article mainly introduces JavaScript how to detect the attributes of the object, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, let the editor take you to understand it.

Detect attributes in an object

This technique is useful when you need to check the existence of certain properties to avoid running undefined functions or properties. If you plan to write cross-browser code, you may also use this technique. For example, let's assume that you need to write code that is compatible with the old version of Internet Explorer 6, and you want to use document.querySelector () to get some elements through ID. However, in modern browsers, this function does not exist. So, to check whether this function exists, you can use the in operator. Take a look at this example:

If ('querySelector' in document) {document.querySelector ("# id");} else {document.getElementById ("id");}

In this case, if there is no querySelector function in document, it uses document.getElementById () instead.

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