JavaScript Syntax

JavaScript is a dynamic and lightweight computer programming language. It is used to generate dynamic client-side pages. It is a cross-platform, open-source language.

Syntax

<script>document.write("___contents here____");</script>

JavaScript syntax is the collection of principles that govern how JavaScript programs are built:

// Variable declaration
var x;

// Assign value to the variable
x = 6;

JavaScript syntax is the collection of principles that define a properly constructed JavaScript program. A JavaScript is made up of JavaScript statements that are inserted within the <script></script> HTML elements on a web page, or in an external JavaScript file with the .js extension.

JavaScript Variables

A JavaScript variable is just the name of the storage place where data will be kept. Variables in JavaScript are classified into two categories, which are listed below:

Local variables: Declare a variable inside the scope of a block.
Global variables: Declare a variable outside of a function or with the help of a window object.

Example

<!DOCTYPE html>
<html>
<body>

<h1>JavaScript Variables</h1>
<p id="demo"></p>

<script>
var name = "Webtutor.dev";
document.getElementById("demo").innerHTML = name;
</script>

</body>
</html>

Preview

JavaScript Operator

JavaScript operators are symbols that can be used to compute values or to perform operations on operands. Arithmetic operators (+, -, *, /) are used to compute values, whereas assignment operators (=, +=, %=) are used to assign values to variables.

Example

<!DOCTYPE html>
<html>
<body>

<h1>JavaScript Operator</h1>

<script>
var x = 5;
var y = 10;
var sum = x + y;
document.write(sum)
</script>

</body>
</html>

Preview

JavaScript Expression

Expressions are made up of values, operators, and variables. It's used to calculate the values.

Example

<!DOCTYPE html>
<html>
<body>

<h1>JavaScript Expression</h1>
<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML = 5 * 10;
</script>

</body>
</html>

Preview

JavaScript Keyword

In JavaScript, keywords are reserved words with special meaning.

Example

<!DOCTYPE html>
<html>
<body>

<h1>JavaScript Keyword</h1>
<p id="demo"></p>

<script>
let x, y;
x = 5 + 10;
y = x * 20;
document.getElementById("demo").innerHTML = y;
</script>

</body>
</html>

Preview

JavaScript Comments

The JavaScript compiler ignores the comments. It improves the readability of the code. It includes code recommendations, information, and warnings. Anything typed after double slashes // (single line comment) or between /* and */ (multi-line comment) is considered as a comment by the JavaScript compiler and ignored.

Example

<!DOCTYPE html>
<html>
<body>

<h1>JavaScript Comments</h1>
<p id="demo"></p>

<script>
let x;
x = 5;
// x = 10;
document.getElementById("demo").innerHTML = x;
</script>

</body>
</html>

Preview

JavaScript Data Types

JavaScript supports many data types for storing distinct values on variables. Because JavaScript is a dynamic programming language, the type of variable does not need to be specified.

In JavaScript, there are two kinds of data types.

Primitive data type
Non-primitive (reference) data type

Example

<!DOCTYPE html>
<html>
<body>

<h1>JavaScript Data Types</h1>

<script>
var name = "Webtutor.dev";
var x = 10;
var lang = ["HTML", "CSS", "JS"];

document.write(typeof name);
document.write(typeof x);
document.write(typeof lang);
</script>

</body>
</html>

Preview

JavaScript Functions

JavaScript functions are chunks of code that are used to accomplish certain activities. When anything calls a JavaScript function, it gets executed. It invokes the method several times, making it reusable.

Example

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Function</h2>
<p id="demo"></p>

<script>
function myFunction() {
    var name = "Webtutor.dev";
    document.write(name);
}
myFunction()
</script>

</body>
</html>

Preview

JS Output

JS Comments

JavaScript Syntax

Syntax

JavaScript Variables

Example

JavaScript Operator

Example

JavaScript Expression

Example

JavaScript Keyword

Example

JavaScript Comments

Example

JavaScript Data Types

Example

JavaScript Functions

Example

Links

Tutorials

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