How to modify the class attribute in js className

js className Method to modify the class attribute: 1. Modify the class name [p-a-0]; 2. Add another class name [p-a-] while retaining [class="p1"] 0]; 3. The result needs to be deleted [class="addp1"].

The operating environment of this tutorial: Windows 7 system, JavaScript version 1.8.5, DELL G3 computer.

js className Method to modify the class attribute:

1. Modify className

1) Modify the class name to p-a-0

2) On the basis of retaining class="p1" Add another class named p-a-0

2 and delete className

1 ).The result needs to be deleted class="addp1"

Regular expression analysis:

3, Check whether a class already exists in the element

if ( document.getElementById("p").className.match(/(?:^|\s)addp1(?!\S)/) ){
     console.log("11")
}

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