# JS Basics
# Comments
// single line comment
/* multiline comment */` also works within a line: `console.log(/*IGNORED!*/ 5); // Still just prints 5
# Basic Syntax and Logic
- Add a semicolon at the end of each executable statement.
- When you name a variable (or array, function etc.) the first character must be a letter, an underscore (_) or a dollar sign ($). Subsequent characters may be letters, numbers, underscores or dollar signs. Also:
- it can not be one of the keywords (opens new window) that are reserved for JavaScript (like var, if, else, for, break, etc)
- JavaScript is case sensitive
- By convention and for readability JavaScript uses camelCase and PascalCase. (kebap-case is not working)
- what is written inside brackets is evaluated before what is outside them
- statements can be grouped together in code blocks, inside curly brackets {...}.The purpose of code blocks is to define statements to be executed together.
# Reserverd Keywords
abstract, arguments, await*boolean, break, bytecase, catch, char, class, const, continuedebugger, default, delete, do, doubleelse, enum, eval, export, extendsfalse, final, finally, float, for, functiongotoif, implements, import,in, instanceof, int, interfacelet, longnative, new, nullpackage, private, protected, publicreturnshort, static, super, switch, synchronizedthis, throw, throws, transient, true, try, typeofvar, void, volatilewhile, withyield
Also Avoid:
Array, Date, eval, function hasOwnProperty, Infinity, isFinite, isNaN, isPrototypeOf, length, Math, NaN, name, Number, Object, prototype, String, toString, undefined, valueOf
# Data Types
JavaScript is a non-typed Language. When adding a number and a string, JavaScript will treat the number as a string.
| Type | Description |
|---|---|
| numbers | JavaScript has only one type of numbers - it doesn't distinguish between integer and float |
| strings | Any series of characters like "John Doe". Written inside quotes: ‘...’ (preferred) or “...” |
| Boolean | true or false. Convention for Name: isCondition |
| arrays | structure that allows you to store a list of values in one single reference. |
| objects | Constructs that have properties. Everything in JavaScript is an object, and can be stored in a variable |
| and also: | |
| Null | represents the intentional absence of a value, and is represented by the keyword null |
| Undefined | also represents the absence of a value though it has a different use than null |
| Symbol | a newer feature to the language, symbols are unique identifiers, useful in more complex coding. |