Document Object Model And Event Handling — Part 1 MCQs with Explanations

setTimeout() and setInterval() allow you to register a function to be invoked once or repeatedly after a specified amount of time has elapsed.

setTimeout() and setInterval() allow you to register a function to be invoked once or repeatedly after a specified amount of time has elapsed.

The onerror handler method can be registered to be invoked when uncaught JavaScript exceptions occur.

The navigator property is used to obtain browser vendor and version information.

Like setTimeout(), setInterval() returns a value that can be passed to clearInterval() to cancel any future invocations of the scheduled function.

The setTimeout() method of the Window object schedules a function to run after a specified number of milliseconds elapses.

setTimeout() returns a value that can be passed to clearTimeout() to cancel the execution of the scheduled function.

If you call setTimeout() with a time of 0 ms, the function you specify is not invoked right away. Instead, it is placed on a queue to be invoked “as soon as possible” after any currently pending event handlers finish running.

The location property of the Window object refers to a Location object, which represents the current URL of the document displayed in the window, and which also defines methods for making the window load a new document.

The above code always results in a true value.

The Document object has a URL property, which is a static string that holds the URL of the document when it was first loaded.

The location property of a window is a reference to a Location object; it represents the current URL of the document being displayed in that window.

The various properties of the location object are the protocol, host, hostname, port, search, and hash.

The hash property returns the “fragment identifier” portion of the URL, if there is one: a hash mark (#) followed by an element ID.

The urgArgs() function can be used to extract arguments from the search property of a URL .

The decodeURIComponent() is a global function defined by client-side JavaScript.

The replace() method is similar, but it removes the current document from the browsing history before loading the new document. When a script unconditionally loads a new document, the replace() method is often a better choice than assign().

The replace() method is similar, but it removes the current document from the browsing history before loading the new document. When a script unconditionally loads a new document, the replace() method is often a better choice than assign().

The assign() method of the Location object makes the window load and display the document at the URL you specify.

The history property of the Window object refers to the History object for the window.

The above code snippet goes back 2, like clicking the Back button twice.

If a window contains child windows, the browsing histories of the child windows are chronologically interleaved with the history of the main window.

The length property of the History object specifies the number of elements in the browsing history list, but for security reasons scripts are not allowed to access the stored URLs.

The go() method takes an integer argument and can skip any number of pages forward and backward in the history list.

Modern web applications can dynamically alter their own content without loading a new document.

The navigator property of a Window object refers to a Navigator object that contains browser vendor and version number information.

IE supports clientInformation as a vendor-netural synonym for navigator.

In the past, the Navigator object was commonly used by scripts to determine if they were running in Internet Explorer or Netscape. This “browser-sniffing” approach is problematic because it requires constant tweaking as new browsers and new versions of existing browsers are introduced. Today, feature testing is preferred: rather than making assumptions about particular browser versions and their features, you simply test for the feature (i.e., the method or property) you need.

The platform and appVersion can be used for browser sniffing.

The string that the browser sends in its USER-AGENT HTTP header. This property typically contains all the information in appVersion and may contain additional details as well. Like appVersion, there is no standard format. Since this property contains the most information, browser-sniffing code typically uses it.

A single web browser window on your desktop may contain several tabs. Each tab is an independent browsing context.

HTML documents may contain nested documents using an iframe element. An iframe creates a nested browsing context represented by a Window object of its own.

Client-side JavaScript makes very little distinction between windows, tabs, iframes, and frames: they are all browsing contexts, and to JavaScript, they are all Window objects.

Client-side JavaScript makes very little distinction between windows, tabs, iframes, and frames: they are all browsing contexts, and to JavaScript, they are all Window objects.

You can open a new web browser window with the open() method of the Window object. Window.open() loads a specified URL into a new or existing window and returns the Window object that represents that window.

When the first argument of the open() is omitted, the about:blank is opened.

The Window object serves as the global object at the top of the scope chain in client-side JavaScript.

The name property of a Window object holds the name of the frame, if it has one. This property is writable, and scripts can set it as desired.

The fourth argument to open() is useful only when the second argument names an existing window. This fourth argument is a boolean value that indicates whether the URL specified as the first argument should replace the current entry in the window’s browsing history (true) or create a new entry in the window’s browsing history (false). Omitting this argument is the same as passing false.

If a frame is contained within another frame that is contained within a top-level window, that frame can refer to the top-level window as parent.parent.