Javascript Review

Flashcards reviewing key Javascript concepts

JavaScript (JS)

A high-level programming language, one of the core technologies of the World Wide Web, enabling interactive web pages and applications; can be executed on the server and on the client.

Dynamic Programming Language

JavaScript is a dynamic programming language where operations done at compile-time can be done at run-time, allowing changes to variable types or adding new properties/methods during program execution.

Node.js

A server-side JavaScript runtime built on the Chrome V8 JavaScript engine, including the NPM package manager for installing node packages.

Identifiers

A sequence of characters identifying a variable, function, or property in code; case-sensitive and can contain Unicode letters, $, _, and digits (0-9), but cannot start with a digit.

Variable Values

Variables store data values; non-primitive values are references. Undefined variables are declared but not assigned, while undeclared variables haven't been declared at all.

Variable Declaration Keywords

let, const, and var are used to declare variables. Let allows reassignment, const does not allow modification after assignment and var defines a variable in the function scope regardless of block scope.

Variable Scopes

Global scope is outside any function or block. Functional scope is within a function. Block scope is for variables declared with let and const.

Dynamic Typing

Variables in JavaScript can be assigned and re-assigned values of all types (number, string, boolean)

Functions

Named list of instructions (statements and expressions). Can take parameters and return a result.

Object Methods

Functions that operate from the context of the object, accessed as a property using dot-notation; JavaScript includes a large standard library.

Arithmetic Operators

Operators that take numerical values as operands and return a single numerical value. Examples: Addition (+), Subtraction (-), Multiplication (), Division (/), Remainder (%), Exponentiation (*).

Assignment Operators

Operators that assign a value to its left operand based on the value of the right operand. Shorthand operators include +=, -=, *=, /=, %=, and **=.

Comparison Operators

Operators used to compare values, including EQUAL (==), EQUAL value and type (===), NOT EQUAL value (!=), NOT EQUAL value or type (!==), GREATER than (>), GREATER than OR EQUAL (>=), LESS than (<), LESS than OR EQUAL (<=).

Truthy and Falsy Values

Values that coerce to true (truthy) or false (falsy) when evaluated in a boolean context. Falsy values include false, null, undefined, NaN, 0, 0n, and "".

Logical Operators

Operators that perform logical operations: && (logical AND), || (logical OR), and ! (logical NOT).

Typeof Operator

An operator that returns a string indicating the type of an operand.

First-class Functions

Functions can be passed as arguments to other functions, returned by other functions, and assigned as a value to a variable.

Nested Functions

Functions that are held within other functions; inner functions have access to variables from their parent functions.

Hoisting

Variable and function declarations are put into memory during the compile phase, but stay where you typed them in your code; only declarations are hoisted.

Debugging - Strict Mode

Strict mode limits certain "sloppy" language features; silent errors will throw Exceptions instead. Enabled by default in modules.