➥ JS Tutorial
- JS HOME
- JS introduction
- JS Where to
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- JS Statements
- JS Syntax
- JS Variables
- JS Operators
- JS Assignment
- JS Data Types
- JS Functions
- JS Objects
- JS Events
- JS Sting methods
- JS String Search
- JS Arrays Methods
- JS Arrays
- JS Sorting Arrays
- JS Array Iteration
- JS Math Object
- JS Comparison & Logical Operators
- JS if else and else if
- JS Switch Statement
- JS For Loop
- JS For In
- JS For Of
- JS While Loop
- JavaScript Break
- JS Sets
- JavaScript typeof
- JS Type Conversion
- JS Bitwise Operations
- JS JSON
- JS Best Practices
- JS Reserved Words
- JS Number Methods
➥ JS Objects
➥ JS Functions
➥ JS Classes
➥ JS HTML DOM
- JavaScript HTML DOM
- JS HTML DOM Document
- JS HTML DOM Elements
- Changing HTML
- JS Forms
- JS HTML DOM - CSS
- DOM Events
- HTML DOM Event Listener
➥ JS Browser BOM
➥ JS Web APIs
➥ JS AJAX
➥ JS JSON
Tutorial
JavaScript Syntax
JavaScript syntax is the set of rules, how JavaScript programs are constructed:
The JavaScript syntax defines two types of values: Fixed values; Variable values. Fixed values are called Literals. Variable values are called Variables.
// How to create variables:
var x;
let y;
// How to use variables:
x = 5;
y = 6;
let z = x + y;
JavaScript Values
The JavaScript syntax defines two types of values:
• Fixed values
• Variable values
Fixed values are called Literals.
Variable values are called Variables.
JavaScript Literals
The two most important syntax rules for fixed values are:
1. Numbers are written with or without decimals:
EXAMPLE ❯
2. Strings are text, written within double or single quotes:
EXAMPLE ❯
JavaScript Variables
In a programming language, variables are used to store data values.
JavaScript uses the keywords var, let and const to declare variables.
An equal sign is used to assign values to variables.
In this example, x is defined as a variable. Then, x is assigned (given) the value 6:
EXAMPLE ❯
JavaScript Operators
JavaScript uses arithmetic operators ( + - * / ) to compute values:
EXAMPLE ❯
JavaScript uses an assignment operator ( = ) to assign values to variables:
EXAMPLE ❯
JavaScript Expressions
An expression is a combination of values, variables, and operators, which computes to a value.
The computation is called an evaluation.
For example, 5 * 10 evaluates to 50:
EXAMPLE ❯
JavaScript Keywords
JavaScript keywords are used to identify actions to be performed.
The let keyword tells the browser to create variables: