jquery cannot see events

In front-end development, we often need to use jQuery, a powerful JavaScript library, which can easily operate on page elements, such as changing styles, adding animations, handling events, etc. However, in actual development, sometimes we may encounter the problem of "jQuery cannot see the event". Even if the event is bound with jQuery, the event cannot be triggered.

So, how does this problem arise? There are usually the following reasons:

1. Code order problem

In some cases, code order problems may occur. For example, we may have manipulated the DOM element before binding the event. As a result, the element has not been loaded when the event is bound, so the event cannot be triggered.

Solution: We can put the code that binds the event and execute it after the DOM element is loaded. You can use methods such as $(window).on('load', function(){ }) or $(document).ready(function(){ }) to ensure that the JS code is executed after the DOM element is loaded.

2. Event delegation problem

When we use event delegation, there may be a problem that the event cannot be triggered. Event delegation refers to binding an event to an ancestor element. When a child element triggers the event, the event will bubble up to the ancestor element and trigger the event bound to the ancestor element.

Solution: First, we need to ensure that the ancestor element of the delegate exists. Additionally, we may need to rebind events to ensure that events are properly delegated to ancestor elements.

3. Element redrawing problem

If we change the style or position of page elements through js, it may cause the element to be redrawn, thereby invalidating previously bound events. .

Solution: We can use delay functions (such as setTimeout) and other methods to bind events after the element is redrawn.

4. Cross-domain issues

When making Ajax cross-domain requests, if the returned data is in JSONP format, there may be a problem that the event cannot be triggered.

Solution: We need to set a callback function on the server side, which will return the data we need, and use jQuery's $.getJSON() method or $.ajax() method on the client side. When making cross-domain requests, set the dataType parameter to 'jsonp'. In this way, the client will automatically pass the callback function name as a parameter to the server. After the server is executed, a callback function similar to "callback(data)" will be returned.

In short, when jQuery cannot see the event, we need to carefully troubleshoot the code, check the above problems, find out the problem and solve it in time. At the same time, in daily development, we should also develop good programming habits, follow code order, standardize event delegation, pay attention to element redrawing, handle cross-domain requests, etc. In this way, higher quality front-end code can be written.

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