Learn jQuery skills to improve your code (I personally think the jquery manual is good) _ jquery

This jQuery selector lab is very cool and can be used online for free. Of course, you can also use it offline locally. This test page contains complex HTML combination fields, and then you can try to use various jQuery selectors predefined. If this is not enough, you can also customize the selector.
2. test whether the jQuery package set contains certain elements.
If you want to test whether a jQuery packaging set contains certain elements, You can first verify whether the first element exists:

The Code is as follows:

If ($ (selector) [0]) {...}
// Or
If ($ (selector). length ){...}

Let's take a look at this example:

The Code is as follows:

// Example. If your page has the following html code

• Item X


• Item Y


• Item Z

...
// This if condition returns true because we have two
// The input field matches the selector, so
 
  
The code will be executed
  
If ($ ('# shopping_cart_items input. in_stock') [0]) {
  
   
}
   

   
 
   
3. Read the latest jQuery version from jquery.org
   
You can use this code to read the code file of the latest jQuery version.