当一个事件发生时(比如单击或者鼠标划过)，捕获阶段就开始了。

When an event occurs (a click or a mouse-over, for example) the capture phase begins.

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事件从捕获阶段开始。

The click event starts in the capturing phase.

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事件从捕获阶段开始。

The click event starts in the capturing phase.

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