How to call event monitoring in jquery

In jQuery, event listening is a common method used to implement the response mechanism of web pages. By listening to a specific event, when the event is triggered, the corresponding code can be executed.

In jQuery, there are two ways to implement event listening: event binding and event delegation. Below we will explain in detail how to use these two methods and the precautions involved.

1. Event binding

Event binding refers to binding an event to an element. When the element triggers the event, the corresponding code will be executed. In jQuery, event binding can use the on() method or bind() method, for example:

$(selector).on(event, function)
$(selector).bind(event, function)

where selector represents the element to which the event is to be bound, event represents the event to be bound, and function represents the event. The function to be executed when triggered. For example, to bind a click event to the element with the id of test, and trigger an alert box when the element is clicked, you can write like this:

$('#test').on('click', function() {
    alert('click');
});

Notes:

1. Event binding Multiple events can be bound, and multiple different events can be bound at the same time.
2. If multiple events are bound to an element and the events have the same handler, then this handler will be called multiple times when the event is triggered.
3. If the bound element is dynamically generated, event delegation is required for correct execution.

2. Event delegation

Event delegation refers to binding an event to an ancestor element. When a descendant element in the ancestor element triggers the event, the corresponding event will be executed. code. In jQuery, you can use the on() method or delegate() method to implement event delegation, for example:

$(ancestorSelector).on(event, descendantSelector, function)
$(ancestorSelector).delegate(descendantSelector, event, function)

Among them, ancestorSelector represents the selector of the ancestor element, descendantSelector represents the selector of the descendant element, and event represents the selector of the descendant element. The bound event, function, represents the function to be executed when the event is triggered. For example, to bind click events to all a tags under the element with the id of test, and trigger an alert box when the a tag is clicked, you can write like this:

$('#test').on('click', 'a', function() {
    alert('click');
});

Notes:

1. Event delegation can reduce the number of binding events and improve the efficiency of binding events.
2. Event delegation can only work when ancestor elements exist.
3. The effect of event delegation may cause some unnecessary effects. For example, all descendant elements under the ancestor element will be affected by the event.

Summary:

Whether using event binding or event delegation, you need to pay attention to the following points:

1. The use of selectors must be accurate. Otherwise, the event may not be bound correctly.
2. The usage scenarios of event binding and event delegation should be determined based on the actual situation.
3. The optimization techniques of event binding and event delegation need to be considered based on the specific situation to achieve the optimal binding effect.

Through the introduction of event monitoring in jQuery and the explanation of its usage, I believe that readers have mastered the skills of how to use jQuery for event monitoring, and also understand the matters that need to be paid attention to in practical applications. , I hope it can be helpful to readers’ learning and development practices.

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