The custom functions in JavaScript are user-defined functions. JavaScript allows us to write our own functions. The following is the syntax −Syntax     Bult-in functions are functions already provided by JavaScript library, for example, the following are string functions −S. NoMethod & Description1charAt()Returns the character at the specified index.2charCodeAt()Returns a number indicating the Unicode value of the character at the given index.3concat()Combines the text of two strings and returns a new string.4indexOf()Returns the index within the calling String object of the first occurrence of the specified value, or -1 if not found.ExampleThe following is an example of a built-in ... Read More

Compared to other languages, JavaScript works differently, especially if you get confused between function and methods. In this tutorial, we will learn whether JavaScript functions are object methods. The example written in this tutorial gives you a better idea about the differences and which one is more convenient for us. What are JavaScript Functions? Functions are generally used to define a particular task that we want to perform. It is a set of instructions, and every function has its block of code. Functions can also have parameters by performing desired operations on those parameters. Syntax The syntax for the ... Read More

To manipulate JavaScript’s Date object, you can either use get or set method and properties. For example, to set hours or to get minutes in JavaScript. Once a Date object is created, a number of methods allow you to operate on it. Most methods simply allow you to get and set the year, month, day, hour, minute, second, and millisecond fields of the object, using either local time or UTC (universal, or GMT) time. Here is a list of the methods used to Date and their description. Sr.No Methods & Description 1 date() Returns today's date ... Read More

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");          

You cannot do this with JavaScript since it takes the system time which displays the current date with Date object. However, you can change the current date by changing the timezone as in the following code −Example Live Demo                    var date, offset, nd;          date = new Date();                  document.write("Current: "+date);          utc = date.getTime() + (date.getTimezoneOffset() * 60000);                  // Singapore is GMT+8          offset = 8;                  nd = new Date(utc + (3600000*offset));          document.write("Singapore Time: "+nd.toLocaleString());           Output

This tutorial will teach us to access the matched groups in JavaScript regular expression. The regular expression is the sequence of the character, also called the RegEx, and it is useful to match specific patterns in the string.There can be more than one match for the specific pattern in the string. To get the occurrence of all matches, we have explained the different methods below in this tutorial.We will also see the various usage of the regular expression in this article.Use the ‘g’ flag while creating the RegexWhen we add ‘g’ as the modifier in the regular expression, it searches ... Read More

You cannot skip a character in a capture group. A match is always consecutive, even when it contains things like zero-width assertions.ExampleHowever, you can access the matched groups in a regular expression like the following code −                    var str = "Username akdg_amit";          var myReg = /(?:^|\s)akdg_(.*?)(?:\s|$)/g;                    var res = myReg.exec(str);          document.write(res[1]);                      

To get a JavaScript stack trace, simply add the following in your code. It will display the stack trace −Example Live Demo                    function stackTrace() {             var err = new Error();             return err.stack;          }          console.log(stackTrace());          document.write(stackTrace());                     Stacktrace prints above.     Output

This tutorial teaches us to get a JavaScript stack trace when we throw an exception. Usually, the developer uses the stack trace to identify the errors while executing the program's code. However, we use the stack trace to debug the program.Using the stack trace, we can get knowledge of any kind of exceptions, such as constructor error, naming error, etc., in our program, and we can correct them.Before we approach analyzing the error using the stack trace, we should know how to stack trace works.How does the call stack trace works?The stack is the primary data structure that follows the ... Read More

In this tutorial, we will learn how to catch syntax errors in JavaScript. In JavaScript, we get will errors if we write any mistakes in code. Like, ReferenceError, i.e., when we call a variable that does not exist in our code. TypeError i.e. when we tried to change the value which is immutable or try to use a variable in an appropriate way. SyntaxError i.e. when we tried to interpret invalid code. We will learn more about this error in detail below. What is Syntax Error? A syntax error is thrown when there is a glitch in ... Read More