A final variable can be explicitly initialized only once. A reference variable declared final can never be reassigned to refer to a different object. However, the data within the object can be changed. So, the state of the object can be changed but not the reference. With variables, the final ... Read More

To pop-up a print dialog box using JavaScript, use the print() method. With the dialog box, you can easily set the printing options like which printer to select for printing.This is the dialog box −ExampleYou can try to run the following code to learn how to print a page −Live ... Read More

When we haven’t initialized the instance variables compiler initializes them with default values.For boolean type, the default value is false, for float and double types default values are 0.0 and for remaining primitive types default value is 0.ExampleLive Demopublic class Sample {    int varInt;    float varFloat;    boolean ... Read More

To refresh a page in a web browser like Firefox means reloading the page. It’s quite easy to refresh a page. Follow the below given steps −Open web pageOpen the web page, which you want to refresh.Find Refresh buttonThe refresh button is located on the top right corner of the ... Read More

With HTML, the essentials are doctype declaration, and . But, you will be amazed to know that a valid HTML document can work without the and element. The doctype declaration will come always since it tells and instructs the browser about what the page is about.Let’s see ... Read More

The increment operator increases an integer value by one. Here’s an example where the value of a is incremented twice using the increment operator twiceExampleLive Demo                    var a = 33;          a = ++a;          document.write("++a = ");          result = ++a;          document.write(result);          

To generate a random number, use the JavaScript Math.random() method. Here set the minimum and maximum value and generate a random number between them as in the following code −ExampleLive Demo                    var max = 6          var min = 2          var random = Math.floor(Math.random() * (max - min + 1)) + min;          document.write(random)          

Reserved words cannot be used as JavaScript variables, functions, methods, loop labels, or any object names.Here are the reserved words in JavaScript −abstractElseinstanceofswitchbooleanEnumintsynchronizedbreakExportinterfacethisbyteExtendslongthrowcaseFalsenativethrowscatchFinalnewtransientcharFinallynulltrueclassFloatpackagetryconstForprivatetypeofcontinueFunctionprotectedvardebuggerGotopublicvoiddefaultIfreturnvolatiledeleteimplementsshortwhileDoImportstaticwithdoubleInsuper

To check if a variable exists in JavaScript, you need to check it against null as in the following code. Here, we’re checking the existence of variable myVar −                    var myVar = 20;          if(myVar !== undefined && myVar !== null) {             document.write("Variable exists");          }          

A boolean variable in JavaScript has two values True or False.ExampleYou can try to run the following code to learn how to work with Boolean variables −           35 > 20       Click for result                      function myValue() {             document.getElementById("test").innerHTML = Boolean(35 > 20);          }