How to use event modifier .capture in Vue to implement event processing in the capture phase

Vue is a popular JavaScript framework that provides us with many convenient features to develop front-end applications. One of them is event modifiers, which allow us to easily control the behavior of events. The .capture in the event modifier allows us to capture the processing of the event. This article will introduce how to use the event modifier .capture in Vue to implement event processing in the capture phase.

The event triggering process can be divided into three stages: capture stage, target stage and bubbling stage. The target stage refers to where the event happens to occur, while the bubbling stage propagates events one by one starting from the target element to the parent element. The capture phase is to gradually pass the event from the root node to the target element before it reaches the target element.

By default, the event handling function bound to Vue is executed in the bubbling phase. But sometimes we need to execute event handling functions during the capture phase. At this time we can use the event modifier .capture to achieve this function.

First, we need to add .capture after the event name where the event is bound, indicating that the event needs to be processed in the capture phase. For example:

<div @click.capture="handleClick">Click me</div>

In the above code, we add the .capture modifier to the click event name, indicating that the event needs to be processed in the capture phase. When a div element is clicked, the handleClick function will be executed during the capture phase.

It should be noted that when using the .capture modifier, the event processing function will be executed before the processing function of the sibling element. In other words, event handlers are executed in the opposite order to the propagation direction of the event. For example:

<div>
  <div @click.capture="handleClick1">
    <div @click="handleClick2">Click me</div>
  </div>
</div>

In the above code, we bind a .click event handler on the inner div element, and bind a .click event handler on the outer div element using the .capture modifier function. When the inner div element is clicked, the handleClick1 function will be executed before the handleClick2 function.

If we want to bind the event handler functions of the capture phase and the bubbling phase to the same element, we can use the .capture and .once modifiers at the same time. For example:

<div @click.capture.once="handleClick">Click me</div>

In the above code, we use the .capture and .once modifiers to bind a click event handler function. This function will only be executed once during the capture phase and not during the bubbling phase.

In short, Vue's event modifier is a very convenient feature that can help us better control the behavior of events. When we need to handle events in the capture phase, we can use the .capture modifier to achieve this function. If you need to execute event handling functions in both the capture phase and the bubbling phase at the same time, we can use the .capture and .once modifiers to accomplish this.

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