JavaScript-reference-book

topic 🦧 a basic set of JavaScript knowledge

📚 Syntax

• 📖 Variables:
    ► declaration ► assignment ► var ► let & const ► naming
• 📖 Data types:
    ► strings ► numbers ► booleans ► null ► undefined ► objects ► symbols ► BigInt
• 📖 Variable scope
    ► global ► local ► function ► code block
• 📖 Additionally:
    ► hoisting ► Lexical scope
• 📖 Operators:
    ► arithmetic ► comparison ► logical ► bitwise
• 📖 Literals:
    ► string ► numeric ► boolean ► object

📚 Control flow

• 📖 Conditionals:
    ► if/else ► switch ► ternary operator
• 📖 Loops:
    ► for ► while ► do..while
• 📖 Controls:
    ► break ► continue ► return
• 📖 Exception handling:
    ► try..catch ► throw ► finally

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Console API reference

• console.log( object [, object, ...] ); >> Prints a message to the Console.
• console.dir( {object} ); >> Prints a JSON representation of the specified object.
• console.dirxml( document ); >> Prints an XML representation of the descendants of node.
• console.group( 'label' ); >> Visually groups messages together.
  • console.info( 'log-1' );
  • console.info( 'log-n' );
  • console.groupEnd( 'label' );
• console.count( [label] ); >> Writes the number of times that count() has been invoked with the same label.
• console.table( array [, columns] ); >> Logs an array of objects as a table.
• console.warn( object [, object, ...] ); >> Prints a warning to the Console.
• console.assert( expression, {object} ); >> Writes an error to the console when expression evaluates to false.
• console.error( object [, object, ...] ); >> Prints object to the Console, formats it as an error, and includes a stack trace.
• console.clear(); >> Clears the console.

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📚 Arrays

• 📖 Basics:
    ► declaration ► initialization ► accessing
• 📖 Methods that do not change initial array
  • array search methods
    • ► .indexOf ► .lastIndexOf ► .find ► .findIndex
    • ► .includes ► .some ► .every
  • array conversion methods
    • ► .toString ► .join
    • ► .concat ► .toLocaleString
  • array iteration methods
    • ► .map ► .reduce ► .reduceRight ► .filter
  • array transformation methods
    • ► ► .slice ► .flat ► .flatMap
• 📖 Methods that change initial array:
  • array mutator methods
    • ► .push ► .unshift ► .pop ► .shift
    • ► .splice ► .copyWithin ► .fill
  • array sorting methods
    • ► .reverse ► .sort
• 📖 Other methods:
  • ► Array.isArray
  • ► .forEach
• 📖 Destructuring:\
  • ► syntax ► swapping var
• How to copy an array?

📚 Objects

• 📖 Basics:
    ► obj literals ► constructor func ► classes ► this ► prototype chain ► destructuring
• 📖 Properties:
    ► access ► assignment ► descriptors ► computed prop
• 📖 Methods:
    ► definitions ► this keyword ► chaining
• 📖 "Collection" objects
    ► Map ► Set
• OOP object oriented programming in JS
  • 📖 Inheritance:
      ► patterns ► obj composition
  • 📖 Encapsulation:
      ► getters & setters ► private variables ► closure func
  • 📖 Polymorphism:
      ► overriding ► overloading ► dynamic dispatch

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ECMAScript (or ES) specification.

That is set of rules and guidelines that language must follow in order to be considered compliant with this specification.

2009-2011 ES5 standard

• Strict mode ('use strict') provides more detailed error checking in code and facilitates debugging.

• you cannot use variables without a declaration;
• function parameters cannot have the same names;
• this will not reference a global object by default;
• does not allow using the with construction in the code;
• cleans up variables created with eval;

• Object.keys(), filter(), map(), reduce(),
• JSON support.

2015 ES6 version

• let and const variables appeared, replacing outdated var;
• arrow functions that preserve context;
• syntactic sugar in the form of classes;
• default function arguments;
• promises;
• destruction of objects;
• ES-modules

• keyword export is used for export;
• keywordimport is used for import;
• they can be perceived as parts of constructor from which program is assembled;
• modules are always "use strict" - this is not window, but undefined.

ES2016:

• destruction of arrays;
• includes;
• exponentiation through **;

ES2017:

• Object.values,
• Object.entries;
• async/await;

ES2018:

• finally for promises;
• update in regular expressions;
• spread operator for objects;

ES2019:

• flat, flatMap for arrays;
• fromEntries for objects;
• queueMicrotask() for event-loop

ES2020:

• BigInt;
• Globalthis;
• ??;

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📚 Functions

• 📖 Basics:
    ► declaration ► expression ► arrow func ► anonymous func
• 📖 Parameters @ Arguments:
    ► positional ► default ► rest
    ► arg object ► destructuring ► spreading arg
• 📖 Return:
    ► statement ► values ► implicit
• 📖 Recursion:
    ► recursive func ► base cases
• 📖 Closure:
    ► lexical scope ► closure func
• 📖 Callbacks:
    ► higher-order func ► callback func

📚 Asynchronous

• 📖 Event loop:
  • call stack
      ► any function that's called synchronously
  • microtasks
      ► process.nextTick ► Promise.then ► async function
  • macrotasks
      ► setTimeout(c, 0) ► setImmediate ► setTimeout(c, n) ► setInterval
• 📖 Promises:
    ► syntax ► chaining ► promise.all ► error handling
• 📖 Async/await:
    ► syntax ► error handling ► async generators

📚 Browser API

• 📖 DOM-BOM
    ► DOM manipulation ► Web Storage ► events
• 📖 Web API
    ► XMLHttpRequest ► fetch API
• 📖 Web Workers
    ►

📚 Regular Expressions

  ► regExp syntax ► literals ► constructor

• 📖 RegExp methods:
    ► test() ► match() ► search() ► replace() ► split() ► exec()
• 📖 RegExp patterns:
    ► char classes ► quantifiers ► alternation ► grouping ► flags
• 📖 Meta-characters:
    ► dot, caret, dollar ► brackets

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Statement is a separate command in code that performs a specific action.

 In JavaScript, all instructions can be divided into several categories:

1. declaration of values

let and const never go out of scope where they were defined and are always initialized where specified;

2. management of execution flow

   if (condition) { "perform certain actions";
   } else { "an alternative scenario takes place"; }

   switch (expression) {
     case value1: 
       statement1
       break;
     case value2: 
       statement2
       break;
     default: 
       statements }

3. iterations

    while (condition) { statement };

    do { statement } while (condition);

   for (initialization; condition; afterthought) { statement };

4. functions
5. others ( debugger, import, export );

Expression is code that returns any value when executed.

 There are 4 ways to execute something in JS:

1. by calling the function;
2. by calling the method of the object (the function is stored in the object);
3. through the constructor function (create new objects of the same type);
4. indirect function call via .call() or .apply();

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