JavaScript determines how to get focus

1. Background

JavaScript is a high-level programming language that is often used to add dynamic interactive effects to web pages. In actual development, it is often necessary to determine whether an element has gained focus in order to perform corresponding operations, such as popping up a prompt box, changing the element style, etc.

2. How to get focus

In JavaScript, you can get the focus of an element in the following two ways:

1. Use the document.activeElement attribute

Document.activeElement is a read-only property of the Document object, which returns the element that has gained focus in the current document. If no element in the current document has focus, this property returns the document itself.

The following is a sample code that can be used to determine whether an element has gained focus:

if(document.activeElement == document.getElementById("myInput")){
    //执行相应的操作
}

2. Use the focus() method

focus( ) method allows an element to gain focus. If the element already has focus, it will have no effect.

The following is a sample code that can be used to determine whether an element has gained focus:

let myInput = document.getElementById("myInput");

if(myInput == document.activeElement){
    //执行相应的操作
}

3. Summary

The ways to determine whether an element has gained focus in JavaScript are: Two ways: using the document.activeElement property and using the focus() method. For scenarios where you need to frequently determine whether an element has gained focus, it is recommended to use the document.activeElement property, because this property can directly return the focused element in the current document. For scenarios where an element needs to gain focus, you can use the focus() method.

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