How can I check if a JavaScript function is defined?

Sravani S
Updated on 23-Jun-2020 06:48:39


To check if a JavaScript function is defined or not, checks it with “undefined”.ExampleYou can try to run the following example to check for a function is defined or not in JavaScript −                    function display() {             alert("Demo Text!");          }          if ( typeof(display) === 'undefined') {             document.write('undefined');          } else {             document.write("Function is defined");          }          

How to debug JavaScript in Visual Studio?

Nancy Den
Updated on 23-Jun-2020 06:47:21

2K+ Views

To debug JavaScript in Visual Studio, follow the below-given steps −Open Visual StudioSelect your project to be debugged in Solution Explorer.Right Click and select Browse With, and set a default browser.Now, go to START and type Internet Options.Above, uncheck both the options for Disable script debugging.Click Apply, and then Ok.Now set breakpoints in your JS file.After that press the debug button in Visual Studio.

What are common HTML Events supported by JavaScript?

Jennifer Nicholas
Updated on 23-Jun-2020 06:45:25


The following are some of the common HTML events supported by JavaScript −AttributeValueDescriptiononclickscriptTriggers on a mouse clickoncontextmenuscriptTriggers when a context menu is triggeredondblclickscriptTriggers on a mouse double-clickondragscriptTriggers when an element is draggedondragendscriptTriggers at the end of a drag operationondragenterscriptTriggers when an element has been dragged to a valid drop targetondragleavescriptTriggers when an element is being dragged over a valid drop targetondragoverscriptTriggers at the start of a drag operationondragstartscriptTriggers at the start of a drag operationondropscriptTriggers when dragged element is being droppedondurationchangescriptTriggers when the length of the media is changed

What are JavaScript Identifiers?

Smita Kapse
Updated on 23-Jun-2020 06:44:09

3K+ Views

JavaScript Identifiers are names given to variables, functions, etc. It is the same as identifiers in other programming languages like C, C++, Java, etc. Let’s see identifiers for variable names.The following are legal variable names −val val1 resultWhile naming your variables in JavaScript, keep the following rules in mind.You should not use any of the JavaScript reserved keywords as a variable name. These keywords are mentioned in the next section. For example, break or boolean variable names are not valid.JavaScript variable names should not start with a numeral (0-9). They must begin with a letter or an underscore character. For ... Read More

How do I get started with Node.js?

Anvi Jain
Updated on 23-Jun-2020 06:41:12


To get started with Node.js, you need to first set its environment. If you are still willing to set up your environment for Node.js, you need the following two software available on your computer, (a) Text Editor and (b) The Node.js binary installable.Let’s see how to install Node.js binary distribution on Windows. Download the latest version of Node.js installable archive file from Node.js official website.Use the MSI file and follow the prompts to install the Node.js. By default, the installer uses the Node.js distribution in “C:\Program Filesodejs”. The installer should set the “C:\Program Filesodejs\bin” directory in the window's PATH environment variable. ... Read More

How do you launch the JavaScript debugger in Google Chrome?

Updated on 23-Jun-2020 06:40:20


To launch JavaScript debugger in Google Chrome, try any of the following ways,Press Ctrl + Shift + JGo to Settings and click More Tools. After that, click Developer Tools.For more, refer the official website of  Chrome Dev Tool,

How to use Custom Exceptions in JavaScript?

Nancy Den
Updated on 23-Jun-2020 06:35:16


Use throw statement in JavaScript, to catch custom exceptions. You can try to run the following to work with custom exceptions −Example                                             Click the following to see the result:                          

How to catch all JavaScript unhandled exceptions?

Rishi Rathor
Updated on 23-Jun-2020 06:34:11


To catch all JavaScript unhandled exceptions, use window.error. The onerror event handler provides three pieces of information to identify the exact nature of the error −Error message − The same message that the browser would display for the given errorURL − The file in which the error occurredLine number− The line number in the given URL that caused the errorExampleYou can try to run the following code to catch unhandled exceptions −                                         Click the following to see the result:                          

How to define custom JavaScript exceptions?

V Jyothi
Updated on 23-Jun-2020 06:33:30


To learn how to define and implement custom JavaScript exceptions, you can try to run the following code −Example                                         Click the following to see the result:                          

What are callback functions in JavaScript?

Nancy Den
Updated on 23-Jun-2020 06:20:32


When a function is passed to another function, it is called a callback function. It goes over this function than to call a passed function.ExampleYou can try to run the following code to learn how to work with callback functions −                    var callback = function(myCallback) {             setTimeout(function() {                myCallback();             }, 5000);          };                    document.write("First is displayed");          document.write("Second is displayed");                    callback(function() {              document.write("This is Callback function");          });          document.write("Last is displayed");