Latest revision as of 07:57, 10 August 2019

Operators[edit | edit source]

'==' or '==='[edit | edit source]

http://es5.github.io/#x11.9.3

iif, .?[edit | edit source]

http://www.whydohow.com/is-there-a-javascript-undefined-property-handling-like-in-angular2-templates/

null-coalescing as logical ||

&& 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 | edit source]

+myString; // convert to number
!!myString; // convert to bool

typeof[edit | edit source]

Array.isArray

Classes[edit | edit source]

В ES6 появляются «настоящие» классы

Strings[edit | edit source]

use Regex where possible

substring

String method substring or slice

last characters

/substring$/.test(str)

last n characters

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

Hashed lists and dictionaries[edit | edit source]

the JavaScript Object is implemented with a hash table

iteration may be done by for(let key in dict)

Set object with very bad support

Remove property from object[edit | edit source]

delete myObject.regex

Arrays[edit | edit source]

contains[edit | edit source]

maybe use Array#includes with polyfill from core-js as ECMAScript 7+ proposal
if (list.filter(s => s.Id === element.Id).length > 0)
core-js dict.includes
this.value = !('value' in data) || data.value

indexOf[edit | edit source]

the best!! Array#indexOf
- Array#includes, which does exactly that, is widely supported, and has a polyfill for older browsers. You can also use Array#indexOf, which is less direct, but doesn't require Polyfills for out of date browsers. jQuery offers $.inArray, which is functionally equivalent to Array#indexOf... Lodash: _.includes

join into string[edit | edit source]

analogs: JSON.stringify() or .toString() method from prototype

function(obj){return JSON.stringify(obj)}).join(' '))

map[edit | edit source]

Array.map() not supported in IE < 9 on jQuery: ($.map(array,

var numbers = [1, 4, 9];
var doubles = numbers.map(function(num) {
  return num * 2;
});

// doubles is now [2, 8, 18]

add[edit | edit source]

push or spread of ES6[edit | edit source]

Use the push() function to append to an array... If you want to add the items of one array to another array, you can use Array.concat() that is immutable

several elements that array did not contain[edit | edit source]

list.push(newList.filter(
                   newEl => list.filter(oldEl => oldEl.Id === newEl.Id).length === 0));
//or 
list = list.concat(newList.filter(
                   newEl => list.filter(oldEl => oldEl.Id === newEl.Id).length === 0));

remove[edit | edit source]

How to remove element from array[edit | edit source]

array.splice(index, 1);

How to remove array from other array[edit | edit source]

for (let i = arr.length - 1; i >= 0; i--) {
  const j = toRemove.indexOf(arr[i]);
  if (j >= 0) {
    arr.splice(i, 1);
  }
};

Loops[edit | edit source]

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

Filtering, LINQ[edit | edit source]

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

Methods[edit | edit source]

toFixed[edit | edit source]

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 | edit source]

querySelector[edit | edit source]

good support including Safari 3.1+, or IE8+

getBoundingClientRect[edit | edit source]