Javascript Articles - Page 600 of 671

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");          }          

To include optional function parameters in JavaScript, you can try the following,function myFunc(a, b = 0) {    // function body }ExampleYou can try to run the following code to learn how to include optional function parameters −                    // default is set to 1          function inc(val1, inc = 1) {             return val1 + inc;          }                    document.write(inc(10,10));          document.write("");          document.write(inc(10));          

We can create many JavaScript variables in a single statement using the var, let, and const keywords that are used for declaring variables in JavaScript. Instead of declaring every variable individually, we can chain many variables together with commas (, ) in a single statement. Since JavaScript is a loosely typed language, variables of many data types can be declared in the same sentence as well. Syntax var variable1 = value1, variable2 = value2, variable3 = value3; Here, var is the keyword used for declaring the variables viz: variable1, variable2, variable3 and assigning them the respective values. Example 1 ... Read More

The Date object is a datatype built into the JavaScript language. Date objects are created with the new Date( ) as shown below −new Date( ) new Date(milliseconds) new Date(datestring) new Date(year, month, date[, hour, minute, second, millisecond ])The following method is used to Manipulate Dates in JavaScript −Sr.NoMethod & Description1Date()Returns today's date and time2getDate()Returns the day of the month for the specified date according to local time.3getDay()Returns the day of the week for the specified date according to local time.4getFullYear()Returns the year of the specified date according to local time.5getHours()Returns the hour in the specified date according to local ... Read More

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,

What is a function in JavaScript? The JavaScript equivalent of a process is a function. A process is a series of instructions for carrying out a task or calculating a value. However, a process must accept input and produce a result to be considered a function. Additionally, there should be a clear connection between the input and the output. Follow the syntax below to define a function This tutorial will guide you to learn the way to execute a JavaScript function using its name in a variable. Syntax function functionName( param1, param2, param3 ) { //code } ... Read More

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

If you want another code while working in the same code document, then use comments. Comment the previous code and add the alternative code to test it. After the testing completes, uncomment the previous code. In this way, you can test both the codes. While using comments follow the below rules to create valid comments − Any text between a // and the end of a line is treated as a comment and is ignored by JavaScript. Any text between the characters /* and */ is treated as a comment. This may span multiple lines. JavaScript also recognizes the ... Read More

Try to keep the length of lines less than 80 characters. This would make the code easier to read. Best practice is to move to next line using break if JavaScript statements aren’t fitting in a single line.In addition, move to next line only after a comma or operator. For example, you can add statement like this, with a break after operator,function display() {    var a = "";    a = a + isNaN(6234) + ": 6234";        a = a + isNaN(-52.1) + ": -52.1";    a = a + isNaN('') + ": ''";    document.getElementById("test").innerHTML = a; }

In this tutorial, we will learn how to name JavaScript Identifiers. Identifiers in JavaScript are the names we give to variables, arrays, objects, functions, etc We must give the names unique to identify them properly. There are some rules we must follow to name the identifiers that are common to most languages. Rules for naming Identifiers There are certain rules we have to follow before naming an identifier. A proper name helps the programmer to make the code more effective. The rules are the following − JavaScript identifier names should not start with any numeric values like 0-9. For ... Read More