Detailed explanation of preventdefault() usage

preventdefault() usage is to handle mouse events or keyboard events. This method can prevent the default behavior of the event, such as preventing the automatic submission of the form, preventing the jump of the link, etc.

preventDefault() is a JavaScript method commonly used to handle mouse events or keyboard events. This method can prevent the default behavior of the event, such as preventing the automatic submission of the form, preventing the jump of the link, etc. This is very useful for our custom event handlers because it prevents the browser's default behavior from interrupting the flow of our program.

Here are some examples of using preventDefault():

Prevent automatic submission of forms:

document.getElementById('myForm').addEventListener('submit', function(event) {  
  event.preventDefault();  
  // do some validation or other processing  
});

In this example, when the form attempts to submit, the preventDefault() method Will prevent the default form submission behavior so we can perform our own validation or other processing.

Prevent link jumps:

document.getElementById('myLink').addEventListener('click', function(event) {  
  event.preventDefault();  
  // do something else, like opening a popup or redirecting to another page  
});

In this example, when the user clicks on the link, the preventDefault() method will prevent the default link jump behavior, so that we can perform our own Code, such as opening a popup window or redirecting to another page.

It should be noted that the preventDefault() method can only be used in event handlers. If you try to call it outside of the event handler, it will have no effect. Additionally, if the event has already been canceled, calling the preventDefault() method again will have no effect.

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