JS Basics Archives | JS FAQ - JavaScript Guides Online

Build-time DEBUG constant: build tools replace DEBUG true/false so optimizer removes dead branches. Use if(false) for local drops. Replace debugHook with a no-op for hot paths. Use integer bitmask FLAGS (e.g. RENDER) for cheap runtime checks.

JS Basics

How to write multiline code in JavaScript

JS Basicsformatting, js basics, multiline, semicolons

Template literals in JavaScript enhance coding style by allowing embedded expressions for calculations and functions within strings. They improve code conciseness, readability, and performance while enabling conditional logic and tagged templates for customized processing. Considerations regarding performance in complex scenarios should be evaluated.

JS Basics

How to use assignment operators in JavaScript

JS Basicsassignment, hello world, js basics

Common pitfalls with assignment operators include confusing equality (==, ===) with assignment (=), unintended reference copying in objects and arrays, and side effects in compound assignments. Proper initialization, cloning, and avoiding nested assignments improve code clarity and prevent bugs.

JS Basics

How to use arithmetic operators in JavaScript

JS Basicsarithmetic, hello world, js basics, math

Operator precedence in JavaScript determines the order of operations in expressions, impacting calculation outcomes. Multiplication and division execute before addition and subtraction. Parentheses clarify operation order, while increment and decrement operators have distinct prefix and postfix behaviors affecting evaluation.

JS Basics

How to declare constants in JavaScript

JS Basicsconst, declaration, js basics, variables

Defining constants in code with const enhances predictability and maintainability. Ideal for primitive values, const signals intent and prevents accidental reassignment. Use uppercase naming for clarity. Consider Object.freeze() for immutability in configuration objects, and avoid var for better scoping. Separate constants into dedicated modules for easier management.

JS Basics

How to run JavaScript in the browser

JS Basicsbrowser, console, devtools, js basics

Browser console enables real-time JavaScript execution, debugging, and DOM inspection with features like console.log(), console.table(), console.group(), and console.trace(). Supports async stack traces, command history, tab completion, and reusable snippets for efficient web development and troubleshooting.

JS Basics

How to include JavaScript in an HTML file

JS Basicsembed, html, js basics, script tag

Add JavaScript to HTML with inline or external script tags. To prevent render-blocking and improve page load speed, place scripts before the closing body tag. For optimal performance, use the defer attribute for ordered execution or async for independent third-party scripts in the head.

JS Basics

How to write your first JavaScript program

JS Basicsbasics, hello world, intro, js basics

JavaScript's single-threaded, synchronous execution model. The call stack, execution context, and blocking behavior. Foundation for asynchronous JS patterns.