This time I will show you how to use JS to determine whether a variable exists, and what are the precautions for using JS to determine whether a variable exists. The following is a practical case, let's take a look.
I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!Recommended reading:
How to implement a custom multi-select event in WeChat applet When select is not used How to implement the drop-down box function under vueThe above is the detailed content of How to use JS to determine whether a variable exists. For more information, please follow other related articles on the PHP Chinese website!