Learn Javascript from Scratch - JS Tutorial for beginners

Explore JavaScript syntax, including statements, blocks with curly braces, and optional semicolons (but always add them), and learn how white space and case sensitivity affect code.

Explain how comments in JavaScript work, including single-line (//) and block (/* ... */) formats, and show how comments clarify code and guide future readers.

Explore how variables act as symbolic names for values. Use placeholders like email and password and apply legal identifiers with alphanumeric, underscore, and dollar signs in JavaScript, noting case sensitivity.

Learn how to declare variables in javascript using the var keyword, without a keyword creating a global variable, and the let keyword from es2015.

Learn how to declare and instantiate a variable in JavaScript using var, assign values, and test results in a Firefox scratchpad with console log.

Explains how let variables cannot be redeclared in the same scope, contrasts let with var mutability, and shows memory storage, block scope, and declaring without a keyword.

Learn how undefined variables occur when a variable is declared but not initialized, and how reference errors arise when accessing non-existent variables. Explore hoisting, let, and var behaviors with examples.

Learn how null behaves in JavaScript by treating it as zero in arithmetic, with examples like null times 10000 equals 0 and null plus 10000 equals 10000.

Explore how variable scoping in JavaScript distinguishes local and global variables, showing how blocks like if statements and the var keyword define scope and accessibility by any function.

Explore var, let, and const in JavaScript scoping, showing var accessible outside blocks, let is block-local, and how undeclared variables trigger reference errors.

Explore JavaScript variable and function hoisting, including how variables are raised to the top and may be undefined, and how named functions hoist while anonymous ones do not.

Explore variable hoisting in JavaScript by examining undefined values, memory persistence in the browser, and how functions are hoisted to the top.

Learn about function hoisting in JavaScript by calling a function before its declaration, see how declaring variables at the top before use prevents undefined values, and avoid crashes.

Explore how not a number can appear in a function's output and how reinserting that value inside the function affects the result. Observe how you might get 15.

Learn how the const declaration creates a read-only reference to a value, meaning the identifier cannot be reassigned within a block and must be initialized at declaration.

Explore how const operates in block scope using an if block, and learn why redeclaring the same identifier with const, let, or a function triggers errors.

Explore how const serves as a block-level variable in javascript, using uppercase naming conventions, and how the same constant can be redeclared in separate blocks with different values.

Learn that declaring an object with const does not protect its attributes; you can change individual properties, like names in a credential list, even though the object reference is constant.

Explore JavaScript data types, including primitive types such as number, string, boolean, null, undefined, and symbol, and how objects store key-value data.

Discover how JavaScript is dynamically typed, allowing a variable to change from string to number without errors, and understand string literals and quotes in practice.

Learn how the plus operator in JavaScript concatenates a number and a string by converting the number to a string, and how other arithmetic operators coerce strings to numbers.

Learn how to convert a string to a number in JavaScript using parseInt, parseFloat, and the unary plus, and see how the plus operator can cause concatenation if not converted.

Learn how to convert strings to numbers in JavaScript with parseInt and a radix, and understand decimal, binary, octal, and hexadecimal bases and digits.

Learn how to convert a string to an integer using a radix, and why always defining the radix matters for hex, decimal, octal, and binary conversions.

Explore how parseInt converts strings to numbers in JavaScript, returning NaN when conversion fails, and how decimal, octal, and binary radices affect the result.

Explore how parseInt uses prefixes like 0x/0X to set radix 16, how 0-prefixed numbers may be octal or decimal depending on the browser, and the ES5 default of 10.

Discover how parseFloat converts strings to floating point numbers, handling decimal points, signs, and exponents, and returns NaN for invalid inputs.

Explore the core literal types in JavaScript, including integer, floating point, and exponential numbers, strings, booleans, arrays, objects, and regular expressions, which are the actual values used in code.

Explore how integer literals use decimal, hexadecimal, octal, and binary bases, and learn how the 0x prefix signals hex and how digits map across bases.

Demonstrate how JavaScript represents integer literals, comparing decimal numbers without a leading zero to octal literals with a leading zero and digits 0–7, and why leading zeros matter.

Understand how JavaScript treats integer literals as octal or decimal based on leading zeros and digits 0-7. For example, 012 equals 10; 8 makes it decimal; remove leading zeros.

Learn how hexadecimal numbers use base 16 with 0x or 0X prefixes, digits 0-9 and a-f, and how leading zeros affect octal interpretation alongside decimal, binary, and hex.

Master integer literals in JavaScript, including binary with 0b/0B, octal with 0, and hexadecimal with 0x/0X, while recognizing decimal defaults and binary-only digits 0 and 1.

Learn how to embed and load JavaScript in HTML emails, using external files or inline scripts, and debug with the browser console and Firebug.

Learn how to output in JavaScript with document.write, console.log, and alert, and how to update the page DOM. Use document.write only for testing, not production.

Learn how to use the web console for debugging by logging information with console.log, explore browser consoles (Chrome, Firefox, Firebug), and understand basic output techniques for JavaScript development.

Use the window alert in JavaScript to display results in an alert box, noting you can call it as window.alert or just alert and still get the same output.

Select an element by its id in the DOM and modify its content to inject text into a targeted heading, illustrating get element by id in practice.

Explore floating point literals in JavaScript, including negative and positive forms, decimal fractions, and exponent notation, and learn that numbers are typically treated as floating point.

Explore string literals in JavaScript by using double or single quotes to enclose characters, understand how quotes create strings, and learn how strings can affect arithmetic through concatenation.

Explore string literals and properties in JavaScript by using the length property to count characters, including spaces, and accessing properties via dot notation on literals and variables.

Learn how template literals perform string interpolation with ${variable} to insert variables without concatenation, and create multiline strings with template syntax.

Learn how template literals enable multiline strings in JavaScript, using backticks to print text across lines, bypass escaping and concatenation, and explore basic interpolation.

Learn how to use template literals for string interpolation in JavaScript, embed expressions with ${}, perform arithmetic inside strings, and avoid tedious concatenation.

Explore how special characters use backslashes to encode within strings, including octal and hexadecimal escapes, with examples like tab and newline. Consult the documentation to learn more escapes.

Learn how to escape characters in JavaScript strings using backslashes to print quotes and spaces. Explore escaping within template literals and see outcomes in the console, avoiding syntax errors.

Explore boolean literals, which have two values: true and false, and learn how falsy values like zero, null, and the empty string affect truth testing.

Learn about array literals in JavaScript, accessible by the array name and an index in square brackets, and how to access elements at a given position.

Learn to create arrays in JavaScript using new Array, populate them or leave empty, and use array literals with square brackets, then access elements by zero-based indexes.

learn how javascript array literals grow dynamically, with elements expanding as you add values and undefineds appearing for gaps. explore contiguous array behavior and how size changes affect subsequent elements.

Declare an array literal with square brackets. Observe that the length property equals the number of elements and updates when you add or remove elements.

Learn how extra and trailing commas affect array literals in JavaScript: extra commas create undefined elements and increase length, while trailing commas are ignored, though they may cause cross-browser issues.

Explore comma examples in array literals, learning how undefined elements affect length, how trailing commas are ignored, and why you should explicitly define undefined elements to avoid issues in browsers.

Explore dynamic array behavior in JavaScript by adding an element at index 20, showing how length expands and intermediate elements become undefined, illustrating sparse arrays.

Learn how JavaScript object literals are collections of properties, where each key pairs with a value; explore real-life examples like tables and cups and creating your own objects.

Access objects with dot or bracket notation to read properties like price from a table object, using table.price or table['price'].

Learn to create objects in JavaScript using object literals, define properties with keys and values, and access them with dot or bracket notation.

Explore object literals in JavaScript, including declaring key value pairs inside curly braces, using dot notation and square brackets to access properties, and nesting objects with varied value types.

Explore object literals in JavaScript, access non-identifier keys with square brackets, and learn that legal identifiers start with a letter or dollar sign but not a number.

Explore regular expression literals in JavaScript, declaring a pattern between slashes, testing text for matches, and returning booleans; learn simple to complex patterns like emails and domain names.

Explore regular expressions as patterns to match characters in strings, test patterns against inputs, and use plus and asterisk to handle repeats, including matching uppercase or lowercase letters.

Explore control flow by examining the order of code execution, including conditional statements, loops, and exceptions; learn to use if-else, switch, and basic loop constructs while handling errors.

Explore conditional statements in JavaScript, including if else blocks and booleans, and understand how true or false conditions drive control flow; preview switch statements in future lessons.

Learn how if else controls program flow, handle falsy values like null, undefined, 0, and empty strings, and chain else if to execute the first true branch.

Master JavaScript conditionals with if and else, learn how true conditions trigger actions and how else provides feedback to prevent silent failures from invalid input.

Explore using an else statement in JavaScript to control flow and provide feedback when conditions fail, including pass/fail logic and range checks 0–100.

Examine compounded else if statements in JavaScript to grade student marks from 0 to 100, assigning 80–100, 60–79, and 0–50, with invalid marks handling.

Learn how compound else if statements assign grades from marks, with range checks for a, b, c, and fail, plus validation for invalid inputs.

Learn how compound else if statements in JavaScript evaluate the first true condition, explore nested if and else blocks, and understand how true conditions determine the resulting grade.

learn how nested if statements work in JavaScript, using a three-number greatest finder with a, b and c, and compare nested ifs to else if and switch concepts.

Explore how the JavaScript switch statement evaluates input and matches it to a case to run code, using break and default as needed.

Explore how the switch statement maps a month variable to January through December using cases, break statements, and a default for invalid values.

Learn a switch-based JavaScript example that uses prompt to collect a user number, adjusts it for zero-based indexing, validates a 1-12 range, and encourages experiments with weeks or other ranges.

Explore switch statements in JavaScript, showing how missing breaks cause fall-through, the role of default for user feedback, and why a break and default improve error handling and UX.