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Browser Default Actions

Browser Events: Browser Default Actions

What is a default action considered in the browser?​

View Answer:
Interview Response: There are several different default actions in the browser. For instance, a click on a link initiates the navigation to the specified URL. Another default action is highlighting text when pressing a mouse button as we glide over the text. As developers, we have control over many of these actions.

Is there a built-in function or method to prevent browser actions?​

View Answer:
Interview Response: Yes, we can use the preventDefault method to prevent specific browser actions.

Code Example:

<a href="/" onclick="return false">Click here</a>
<!-- or -->
<a href="/" onclick="event.preventDefault()">here</a>

What happens when you return a false value from a handler?​

View Answer:
Interview Response: The value returned by an event handler usually gets ignored. The only exception is returning false from a handler assigned on‹event‹. In all other circumstances, the return value gets disregarded, making no sense to return true.

What is the function of the defaultPrevented property?​

View Answer:
Interview Response: The defaultPrevented read-only property of the Event interface returns a Boolean indicating whether the call to Event.preventDefault() canceled the event. The property event.defaultPrevented is true if the default action was prevented and false otherwise.

Code Example:

<p>Right-click for the document menu</p>
<button id="elem">Right-click for the button menu</button>

<script>
  elem.oncontextmenu = function (event) {
    event.preventDefault();
    alert('Button context menu');
  };

  document.oncontextmenu = function (event) {
    if (event.defaultPrevented) return;

    event.preventDefault();
    alert('Document context menu');
  };
</script>