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'==' or '==='[edit]

Крайне рекомендуется использовать только операторы строгого равенства

used in #indexOf

iif, .?[edit]

null-coalescing as logical ||

&&, ||[edit]

&& evaluates as long as the statement is true. If it is true, it returns the last value. If it is false, it returns the first value that evaluated to false. That may be 0, null, false etc. || returns the first value that evaluates to true.

Types casting[edit]

!!myString; // convert to bool

+myString; // convert to number

~~myNumber; // double NOT bitwise operator is faster substitute for Math.floor()

TypeScript vs CSharp[edit]

CSharp to JS migration

any is like dynamic and unknown is like object


  • Array.isArray


use Regex where possible

  • substring

String method substring or slice

  • last characters


  • last n characters

slice.(0, -n) - allows you to make the second argument negative

Hashed lists and dictionaries[edit]

the JavaScript Object is implemented with a hash table iteration may be done by for(let key in dict)

Remove property from object[edit]

delete myObject.regex


Every object (including functions) has this internal property called prototype. It can only be set at object creation time, either with new, with Object.create, or based on the literal (functions default to Function.prototype, numbers to Number.prototype, etc.). It can only be read with Object.getPrototypeOf(someObject). There is no other way to set or read this value... Functions, in addition to the hidden prototype property, also have a property called prototype, and it is this that you can access, and modify


If you want to iterate over an object's keys, use for (var key in object). If you want to iterate over an array’s elements, however, use for(var i = 0; i < array.length; i += 1)

in TypeScript iteration over elements is for(let i of list) construction


  • Array.prototype.filter

good support

  • Array.prototype.find - returns the value of the first element in the array that satisfies the provided testing function

bad support: no IE, Safari 7.1



toFixed() з javascript використовуємо лише для внутрішніх розрахунків, для презентаційних цілей (показати юзеру) її ніззя, бо вона не враховує регіональні налаштування формату чисел

DOM and browser[edit]


good support including Safari 3.1+, or IE8+


good support

Page redirect[edit]

як правильно зробити редірект через window.location

  • GetAppRoot() - кастомна ЖС функція


setTimeout и setInterval... Рекурсивный setTimeout позволяет задать задержку между выполнениями более точно, чем setInterval.[edit]

Event Loop[edit]


bad support, no IE, no Windows 8.1, but polyfilled in core-js

Async functions from iOS versions#10.3


This category has only the following subcategory.


Pages in category "JS coding guide"

The following 6 pages are in this category, out of 6 total.