Операторы JavaScript

Введение

В JavaScript понимание сравнений и операторов имеет решающее значение для эффективного скриптования. Это руководство рассмотрит операторы сравнения, арифметические операции и конкатенацию строк, обеспечивая полное понимание этих основных понятий.

Операторы сравнения JavaScript

Равенство и неравенство

Строгое (===) и нестрогое (==) равенство

Строгое равенство (===) проверяет и значение, и тип, в то время как нестрогое равенство (==) преобразует типы перед сравнением.

// Strict equality
console.log(3 === '3'); // false
// Loose equality
console.log(3 == '3'); // true
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Больше (>) и меньше (<)

Эти операторы используются для сравнения числовых значений.

// Greater than
console.log(5 > 3); // true
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Специальные случаи в сравнениях

Сравнение нечисловых значений

JavaScript выполняет приведение типов, что часто приводит к неожиданным результатам.

// String and boolean comparison
console.log('2' < true); // false
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Сравнения NaN

NaN не равно никакому значению, включая самого себя.

console.log(NaN == NaN); // false
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Арифметические операторы в JavaScript

Базовые операторы: сложение (+), вычитание (-), умножение (*), и деление (/)

Эти операторы используются для базовых арифметических операций.

// Addition
console.log(5 + 3); // 8
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Модуль (%) и возведение в степень (**)

Модуль возвращает остаток от деления, тогда как возведение в степень поднимает число в степень другого.

// Modulus
console.log(10 % 4); // 2
// Exponentiation
console.log(3 ** 2); // 9
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Конкатенация строк и двоичный оператор +

Конкатенация строк

В JavaScript оператор + используется как для числового сложения, так и для конкатенации строк.

// String concatenation
console.log('Hello ' + 'World!'); // Hello World!
// Using template literals
let name = 'Alice';
console.log(`Hello, ${name}!`); // Hello, Alice!
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Двоичный + и приведение типов

Когда один операнд является строкой, JavaScript преобразует другой в строку.

// Binary + with string and number
console.log('3' + 2); // "32"
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Лучшие практики для конкатенации

Используйте шаблонные литералы для ясности и избегания путаницы с числовым сложением.

// Template literal
console.log(`3 + 2 is ${3 + 2}`); // 3 + 2 is 5
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Заключение

Понимание сравнений, арифметических операторов и конкатенации строк является фундаментальным в JavaScript. Эти знания составляют основу многих программных задач, от простых вычислений до сложного процесса принятия решений.

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