Логическое И. Возвращает последний верный операнд

Возвращает последний операнд, если все они верны.

Возвращает последний операнд, если все они верны.

Верно, эффект имеет только использование ||, с && же подобным образом обращение не срабатывает

Спасибо, развернул эту часть статьи чуть пошире.

"+" делает конкатенацию, если хотя бы один операнд - строка, причем, не обязательно первый.

А как же такой красивый способ преобразования к числу?

var s = '7';
var n = +s;
alert(n.constructor); // Number

"...Сравнение == делается с приведением типов, а === без приведения типов...". Наверное, наоборот:Сравнение == делается БЕЗ приведения типов, а === С приведения типов

Мне кто нибудь может подсказать как исчисляется
>>> (Сдвиг вправо с заполнением нулями)
>>>= (Сдвиг вправо с заполнением нулями и присваиванием)
Пытаюсь понять, но никак не получается.
x=13>>>1
x=6
Как они его вычислили, что получилась такая сумма?
Про разряды я то знаю, мне интересно сам ход выполнения операции.

у меня есть строка, скажем "2+2*3". как получить результат вычисления (8) из строки, не разбирая её (длина строки не известна, операторы также)?

Спасибо, очень полезная статья

var y = 0
if (y == (1 || 21 || 31 || 41 || 51 || 61 || 71)) {"тру"} else {"фэил"}//"фэил"
if (y == 1 || 21 || 31 || 41 || 51 || 61 || 71) {"тру"} else {"фэил"}//"тру"

почему второй if выдает "тру" ?
и вообще может это как-то по другому делается?
как написать условие:

if (numRows != 1 и заканчивается на 1) {var p = "заявок заархивированно"}
например numRows = 11 или 21 или 31

Вначале упомянули про оператор <<<, но подробно про него не рассказано.

И результат вырежения "B" > "a" - false, так как прописная 'B' имеет на самом деле меньший код, чем строчная 'a' .

по моему точно что то напутали с типами, как вы обьясните такой пример?

if(1 === String(1)){
alert("одинаковые типы");
}else{
alert("разные типы");
}

отработает else

Вот это правильный вариант произведения сложения двух значений.

function calculate() {
var chislo1 = document.primer.chislo1.value; /присваиваем переменой значение которое было введено
var chislo2 = document.primer.chislo2.value;
var x = +chislo1;
var y = +chislo2;
var z = x + y;
if (isFinite(z)) {
resultat.innerHTML = z.toFixed(2);
}
else {
res1.innerHTML = "ошибка";
}

}

по поводу сравнения строк: стоит добавить, что "лексикографически" подразумевает под собой сравнение по номеру в таблице юникод, т.е.

"B">"a" //false, т.к. \u0042 < \u0061
"bc" < "bd"  // true

а кирилличные символы вообще далеко в таблице, поэтому

"Щ">"z" //true

а какой-нибудь u\263a вообще больше почти всего

"☺">"я" //true

здесь в учебнике это подробно описано

можно подробнее описать дейсвие ?

действие-?-этого знака

В Javascript есть все необходимые для жизни операторы, хотя нет их перегрузки.

Я бы не сказал.

function Point (x,y) {
this.x = x;
this.y = y;
this.toString = function() {
return "Point( " + this.x + ", " + this.y + " )";
}
return this;
}

var foo = new Point(2, 3);
alert( "Foo is " + foo ); // Выдаст "Foo is Point( 2, 3 ) "

Здесь в alert() вызывается foo.toString() при складывании foo и "Foo is". Это почти перегрузка оператора приведения типов, как в С++:

#include
#include
#include

using namespace std;

struct Point {
int x, y;
operator const char* () {
stringstream s;
s << "Point( " << x << ", " << y << " )";
return s.str().c_str();
}
};

int main() {
Point p = {2,3};
cout << "Hello Point: " << p;
}

Приведение типов можно перегрузить! Я не очень понимаю почему это происходит, но это работает.

Если быть совсем точным, то "И" возвращает первый операнд, если он неверен, иначе - второй.
А "ИЛИ" возвращает первый операнд, если он верен, иначе - второй.

Что означает код:
for(var y = 0; y <= 33; y++) {
y == 0 && SomeClass.Foo();
}

Цикл мне понятен. Не понятно значение && в этом контексте, т.е. если y == 0 и тогда выполняется некоторая функция класса SomeClass.Foo() ?
А если y != 0 тогда функция не будет выполняться?

Внезапно в Опере: "Текст" + chislo&256 даёт 0. Пришлось выкручиваться: "Текст" + String(chislo&256)

Подскажите мне, почему в данном коде не возвращает false, как это указано в статье? Вот, берем объект БЕЗ свойства rabbit и получаем прогнозируемый undefined (но никак не false, как указано в статье):

var petShop = {animals:5,pet:5};

var rabbit = petShop && petShop.animals && petShop.animals.rabbit;
alert (rabbit);//=>undefined (а не false, как говорится в статье)

var rabbit = petShop.animals.rabbit;
alert (rabbit);//=>undefined (какой смысл тогда применять прием по поиску свойства в объекте с использованием &&? )

вот еще код к вопросу... просто не могу понять, зачем прием с && при проверке
petShop.animals.rabbit, ведь результат не меняется:

var petShop = {animals:5, pet:5};
if (petShop && petShop.animals && petShop.animals.rabbit) {
alert('тут true');
} else { alert('попадаем в false');}//ушли в false

if (petShop.animals.rabbit) {alert('тут true');
} else { alert('ушли в false снова');}//ушли в false

var petShop = {animals:{rabbit:9}, pet:5}; if (petShop && petShop.animals && petShop.animals.rabbit) {alert('тут true');// тут true
} else { alert('попадаем в false');}//

if (petShop.animals.rabbit) {alert('тут true');// тут true
} else { alert('ушли в false снова');}

//в чем тогда разница-то? Зачем if (petShop && petShop.animals && petShop.animals.rabbit), а не просто if (petShop.animals.rabbit)

Просьба пояснить, что значит данная конструкция?
var toggle = oldop == 'upload';

Кто нибудь объясните плиз логику работы ' % '.
Написано что возвращает остаток от деления. Но :

function myFunction() {
for ( var i=1; i<140; ++i){
var x =100 % i;
console.log(", " +x);
}

:Вывод> , 0, 0, 1, 0, 0, 4, 2, 4, 1, 0, 1, 4, 9, 2, 10, 4, 15, 10, 5, 0, 16, 12, 8, 4, 0, 22, 19, 16, 13, 10, 7, 4, 1, 32, 30, 28, 26, 24, 22, 20, 18, 16, 14, 12, 10, 8, 6, 4, 2, 0, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100

Это вообще что ?

window.alert("вот вот")

Information about Operators, their features in JS are very good and very helpful for me at work, the information is very useful. Please continue to uphold.
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