Скачать или смотреть How to Run a JavaScript Function on Click of Dropdown Menu Without Re-triggering on Selection

Learn how to effectively run a JavaScript function when a dropdown menu is clicked and prevent it from running again upon selection in this easy-to-follow guide.
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This video is based on the question https://stackoverflow.com/q/70036225/ asked by the user 'MarkoZg' ( https://stackoverflow.com/u/11565514/ ) and on the answer https://stackoverflow.com/a/70036299/ provided by the user 'mplungjan' ( https://stackoverflow.com/u/295783/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem: JavaScript Dropdown Menus

In web development, dropdown menus are commonly used for user selections. However, there may be instances when you want to trigger a JavaScript function only when the dropdown is clicked and not again once an option is selected. This can help create a smoother user experience and avoid unnecessary executions of your script.

The Challenge

The challenge arises when you have a dropdown menu that executes a function both when the dropdown is clicked and when an option is selected. If you want your code to run only on the dropdown click (triggered before any options are selected), you'll need to differentiate between these two actions: the click event and the selection event.

Solution: Using JavaScript Events to Handle Clicks

The Key Concept: Understanding Mouse Events

The solution lies in using two different mouse events: mousedown and click. Here’s how these work:

mousedown: This event is triggered as soon as the mouse button is pressed down on the dropdown menu.

click: This event is triggered after the mouse button is released, which means if a user clicks and holds the mouse, only the mousedown event is captured until they release it.

Implementation Steps

To implement this functionality, you can use jQuery to listen for the mousedown event instead of just the click event. Follow these steps:

Include jQuery: If you haven’t already, include jQuery in your HTML to easily handle events.

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Identify Your Dropdown: Ensure your dropdown has a unique ID for selection.

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Implement the Event Handlers: Add the following JavaScript code using jQuery to capture the desired events.

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Explanation of the Code

The first event listener captures the mousedown event, triggering your function only when the dropdown is clicked and not when an item is selected.

The click event captures when the user releases the mouse button, allowing for separate actions if needed.

Conclusion

With this approach, you can effectively run a JavaScript function only when a dropdown menu is clicked, and prevent any further executions when options are selected. This method not only optimizes the user experience but also ensures that your scripts run at the right times. Implement these steps, and you’ll master dropdown interactions in no time!