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среда, 4 мая 2022 г.

Что означает этот символ в JavaScript?








Решение проблемы

См. документацию по MDN о выражениях, операторах и операторах.

Основные ключевые слова и общие выражения

thisключевое слово:

  • Как работает ключевое слово «это»?

  • var x = function()vs. function x()  — Синтаксис объявления функции

  • var имя_функции = имя_функции () {} vs имя_функции () {}

  • (function(){})()  — IIFE (выражение немедленно вызываемой функции)

  • Какова цель? , Как это называется?

  • Почему (function(){…})();работает, но function(){…}();не работает?

  • (function(){…})();против(function(){…}());

  • более короткие варианты:
  • !function(){…}();- Что делает восклицательный знак перед функцией?

  • +function(){…}();- Знак плюса JavaScript перед выражением функции

  • !function(){ }() vs (function(){ })(), !vs точка с запятой в начале


  • (function(window, undefined){…}(window));

  • someFunction()()  — Функции, которые возвращают другие функции

  • Два набора скобок после вызова функции

  • =>  — Знак равенства, больше чем: синтаксис выражения стрелочной функции

  • Что означает «=>» (стрелка, образованная из «равно» и «больше») в JavaScript?

  • |>  — Труба, больше чем: оператор конвейера

  • Что делает оператор «|>» в JavaScript?

  • function*, yield, yield*  — Звездочка после functionили yield: генераторные функции

  • Что такое «функция*» в JavaScript?

  • Что такое ключевое слово yield в JavaScript?

  • Делегированная доходность (звездочка доходности, доходность *) в функциях-генераторах

  • [], Array()  — Квадратные скобки: запись массива

  • В чем разница между «Array()» и «[]» при объявлении массива JavaScript?

  • What is array literal notation in javascript and when should you use it?

  • If the square brackets appear on the left side of an assignment ([a] =...), or inside a function's parameters, it's a destructuring assignment.

    {key: value}  —  Curly brackets: object literal syntax (not to be confused with blocks)

  • What do curly braces in JavaScript mean?

  • Javascript object literal: what exactly is {a, b, c}?

  • What do square brackets around a property name in an object literal mean?

  • If the curly brackets appear on the left side of an assignment ({ a } =...) or inside a function's parameters, it's a destructuring assignment.

    `${}`  —  Backticks, dollar sign with curly brackets: template literals

  • What does this `…${…}…` code from the node docs mean?

  • Usage of the backtick character (`) in JavaScript?

  • What is the purpose of template literals (backticks) following a function in ES6?

  • //  —  Slashes: regular expression literals

  • Meaning of javascript text between two slashes

  • $  —  Dollar sign in regex replace patterns: $$, $&, $`, $', $n

  • JavaScript replace() method dollar signs

  • ()  —  Parentheses: grouping operator

  • MDN: Grouping operator

  • Property-related expressions

    obj.prop, obj[prop], obj["prop"]  —  Square brackets or dot: property accessors

  • JavaScript property access: dot notation vs. brackets?

  • ?., ?.[], ?.()  —  Question mark, dot: optional chaining operator

  • Question mark after parameter

  • Null-safe property access (and conditional assignment) in ES6/2015

  • Optional Chaining in JavaScript

  • Is there a null-coalescing (Elvis) operator or safe navigation operator in javascript?

  • Is there a "null coalescing" operator in JavaScript?

  • ::  —  Double colon: bind operator

  • JavaScript double colon (bind operator)

  • new operator

  • What is the 'new' keyword in JavaScript?

  • What is "new.target"?

  • ...iter  —  Three dots: spread syntax; rest parameters

  • (...rest) => {}  —  What is the meaning of "…args" (three dots) in a function definition?

  • fn(...args)  —  What is the meaning of "foo(…arg)" (three dots in a function call)?

  • [...iter]  —  javascript es6 array feature […data, 0] "spread operator"

  • {...props}  —  Javascript Property with three dots (…), What does the '…rest' stand for in this object destructuring?

  • Increment and decrement

    ++, --  —  Double plus or minus: pre- / post-increment / -decrement operators

  • ++someVariable vs someVariable++ in Javascript

  • Unary and binary (arithmetic, logical, bitwise) operators

    delete operator

  • What is the purpose of the delete operator in Javascript?

  • void operator

  • What does `void 0` mean?

  • +, -  —  Plus and minus: addition or concatenation, and subtraction operators; unary sign operators

  • What does = +_ mean in JavaScript, Single plus operator in javascript

  • What's the significant use of unary plus and minus operators?

  • Why is [1,2] + [3,4] = "1,23,4" in JavaScript?

  • Why does JavaScript handle the plus and minus operators between strings and numbers differently?

  • |, &, ^, ~  —  Single pipe, ampersand, circumflex, tilde: bitwise OR, AND, XOR, & NOT operators

  • What do these JavaScript bitwise operators do?

  • How to: The ~ operator?

  • Is there a & logical operator in Javascript

  • What does the "|" (single pipe) do in JavaScript?

  • What does the operator |= do in JavaScript?

  • What does the ^ (caret) symbol do in JavaScript?

  • Using bitwise OR 0 to floor a number, How does x|0 floor the number in JavaScript?

  • Why does ~1 equal -2?

  • What does ~~ ("double tilde") do in Javascript?

  • How does!!~ (not not tilde/bang bang tilde) alter the result of a 'contains/included' Array method call? (also here and here)

  • %  —  Percent sign: remainder operator

  • What does % do in JavaScript?

  • &&, ||, !  —  Double ampersand, double pipe, exclamation point: logical operators

  • Logical operators in JavaScript — how do you use them?

  • Logical operator || in javascript, 0 stands for Boolean false?

  • What does "var FOO = FOO || {}" (assign a variable or an empty object to that variable) mean in Javascript?, JavaScript OR (||) variable assignment explanation, What does the construct x = x || y mean?

  • Javascript AND operator within assignment

  • What is "x && foo()"? (also here and here)

  • What is the!! (not not) operator in JavaScript?

  • What is an exclamation point in JavaScript?

  • ??  —  Double question mark: nullish-coalescing operator

  • How is the nullish coalescing operator (??) different from the logical OR operator (||) in ECMAScript?

  • Is there a null-coalescing (Elvis) operator or safe navigation operator in javascript?

  • Is there a "null coalescing" operator in JavaScript?

  • **  —  Double star: power operator (exponentiation)

  • x ** 2 is equivalent to Math.pow(x, 2)

  • Is the double asterisk ** a valid JavaScript operator?

  • MDN documentation

  • Equality operators

    ==, ===  —  Equal signs: equality operators

  • Which equals operator (== vs ===) should be used in JavaScript comparisons?

  • How does JS type coercion work?

  • In Javascript, <int-value> == "<int-value>" evaluates to true. Why is it so?

  • [] ==![] evaluates to true

  • Why does "undefined equals false" return false?

  • Why does!new Boolean(false) equals false in JavaScript?

  • Javascript 0 == '0'. Explain this example

  • Why false == "false" is false?

  • !=, !==  —  Exclamation point and equal signs: inequality operators

  • != vs.!==

  • What is the difference between!= and!== operators in JavaScript?

  • Bit shift operators

    <<, >>, >>>  —  Two or three angle brackets: bit shift operators

  • What do these JavaScript bitwise operators do?

  • Double more-than symbol in JavaScript

  • What is the JavaScript >>> operator and how do you use it?

  • Conditional operator

    ?:…  —  Question mark and colon: conditional (ternary) operator

  • Question mark and colon in JavaScript

  • Operator precedence with Javascript Ternary operator

  • How do you use the?: (conditional) operator in JavaScript?

  • Assignment operators

    =  —  Equal sign: assignment operator

  • What is the difference between the `=` and `==` operators and what is `===`? (Single, double, and triple equals)

  • This symbol is also used for default parameters or default values in a destructuring assignment:

  • what does (state = {}) => state means

  • What does ({"key": "value"} = {}) syntax mean inside a JavaScript function

  • %=  —  Percent equals: remainder assignment

  • Having Confusion with Modulo operator

  • +=  —  Plus equals: addition assignment operator

  • How does += (plus equal) work?

  • &&=, ||=, ??=  —  Double ampersand, pipe, or question mark, followed by equal sign: logical assignments

  • What purpose do &&=, ||= and??= serve?

  • Replace a value if null or undefined in JavaScript

  • Set a variable if undefined

  • Ruby's ||= (or equals) in JavaScript?

  • Original proposal

  • Specification

  • Destructuring

  • of function parameters: Where can I get info on the object parameter syntax for JavaScript functions?

  • of arrays: Multiple assignment in javascript? What does [a,b,c] = [1, 2, 3]; mean?

  • of objects/imports: Javascript object bracket notation ({ Navigation } =) on left side of assign

  • Comma operator

    ,  —  Comma operator (not to be confused with the comma used in variable declarations)

  • What does a comma do in JavaScript expressions?

  • Comma operator returns first value instead of second in argument list?

  • When is the comma operator useful?

  • Control flow

    {}  — Curly brackets: blocks (not to be confused with object literal syntax)

  • JavaScript curly braces with no function or json

  • Declarations

    var, let, const  —  Declaring variables

  • What's the difference between using "let" and "var"?

  • Are there constants in JavaScript?

  • What is the temporal dead zone?

  • var a, b;  —  Comma used in variable declarations (not to be confused with the comma operator): JavaScript variable definition: Commas vs. Semicolons

  • Label

    label:  —  Colon: labels

  • What does the JavaScript syntax foo: mean?

  • What does ':' (colon) do in JavaScript?

  • Other

    123n  —  n after integer: BigInt

  • Что означает символ «n» после числового литерала в JavaScript?

  • #  — Хэш (цифровой знак): частные методы или частные поля.

  • Что делает #символ в JavaScript?

  • _  — Подчеркивание: разделитель в числовых литералах

  • Числовые разделители Javascript?

  • Существует ли Javascript, эквивалентный синтаксису Ruby, использующий символы подчеркивания (например, 10_000 = 10000), чтобы сделать большие целые числа удобочитаемыми для человека?

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