REFERENCEjavascript

javascript Documentation

📖 INDEX

# what-is-javascript

# function-declaration

# function-expressions

# anonymous-functions

# arrow-functions

# return

# recursive-functions

# arguments-parameters

# array-destructuring

# what-is-dom

# element-selection

# selection-methods

# elements-manipulation

# events

# event-listeners

# modification-methods

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Basic Syntax

AI & DATA SCIENCE // basic-syntax

JavaScript syntax rules: statements end with semicolons (optional), code blocks use curly braces, identifiers are case-sensitive.

Syntax

// statement
let x = 5;
// block
if (x > 3) {
  console.log('big');
}

Deep Dive Course

A JavaScript program is made up of **statements** separated by semicolons. Code blocks `{}` group statements. Identifiers are **case-sensitive** (`myVar !== myvar`). Whitespace is ignored except inside strings.

1Understanding Basic Syntax

A JavaScript program is made up of statements separated by semicolons. Code blocks {} group statements. Identifiers are case-sensitive (myVar !== myvar). Whitespace is ignored except inside strings.

💡

Semicolons are optional due to ASI (Automatic Semicolon Insertion), but explicit semicolons prevent ambiguity bugs.

editor.html

// Statements and blocks
let name = 'Alice';
let age  = 30;

if (age >= 18) {
  console.log(name + ' is an adult');
}

localhost:3000

2Practical Example

Here is a real-world application of Basic Syntax showing how it is used in production JavaScript code.

editor.html

// Case sensitivity
let myVar = 1;
let myvar = 2;
console.log(myVar); // 1
console.log(myvar); // 2

localhost:3000

3Best Practices

Follow these guidelines when working with Basic Syntax:

1. Always use curly braces for if/else blocks

2. Consistent indentation (2 or 4 spaces)

3. One statement per line

⚠️

Tip: Semicolons are optional due to ASI (Automatic Semicolon Insertion), but explicit semicolons prevent ambiguity bugs.

editor.html

// Statements and blocks
let name = 'Alice';
let age  = 30;

if (age >= 18) {
  console.log(name + ' is an adult');
}

localhost:3000

Examples

Example 01Basic Usage

// Statements and blocks
let name = 'Alice';
let age  = 30;

if (age >= 18) {
  console.log(name + ' is an adult');
}

Example 02Advanced Example

// Case sensitivity
let myVar = 1;
let myvar = 2;
console.log(myVar); // 1
console.log(myvar); // 2

Best Practices

Always use curly braces for if/else blocks
Consistent indentation (2 or 4 spaces)
One statement per line

Interview Question

What is ASI in JavaScript?▼

Hint: Automatic Semicolon Insertion.

ASI is a JavaScript parser feature that automatically inserts semicolons at line ends in certain cases. It can cause subtle bugs — e.g., a return on one line and a value on the next returns undefined.

Exercises

MediumPractice using Basic Syntax in a real scenario.

View Solution

// Statements and blocks
let name = 'Alice';
let age  = 30;

if (age >= 18) {
  console.log(name + ' is an adult');
}

Frequently Asked Questions

What is ASI in JavaScript?▼

Related Functions

VariablesCommentsOperators