JavaScript 运算符

JavaScript 运算符是执行一个或多个操作数（值）的特殊符号。例如，

2 + 3;  // 5

这里，我们使用 + 运算符将操作数 2 和 3 相加。

JavaScript 运算符类型

以下是本教程中将介绍的各种 JavaScript 运算符列表

1. 算术运算符
2. 赋值运算符
3. 比较运算符
4. 逻辑运算符
5. 位运算符
6. 字符串运算符
7. 杂项运算符

1. JavaScript 算术运算符

我们使用算术运算符执行算术计算，如加法、减法等。例如，

5 - 3;  // 2

这里，我们使用 - 运算符从 5 中减去 3。

常用算术运算符

示例 1：JavaScript 中的算术运算符

let x = 5;

// addition operator
console.log("Addition: x + 3 = ", x + 3);

// subtraction operator
console.log("Subtraction: x - 3 =", x - 3);

// multiplication operator
console.log("Multiplication: x * 3 =", x * 3);

// division operator
console.log("Division: x / 3 =", x / 3);

// remainder operator
console.log("Remainder: x % 3 =", x % 3);

// increment operator
console.log("Increment: ++x =", ++x);

// decrement operator
console.log("Decrement: --x =", --x);

// exponentiation operator
console.log("Exponentiation: x ** 3 =", x ** 3);

输出

Addition: x + 3 =  8
Subtraction: x - 3 = 2
Multiplication: x * 3 = 15
Division: x / 3 = 1.6666666666666667
Remainder: x % 3 = 2
Increment: ++x = 6
Decrement: --x = 5
Exponentiation: x ** 3 = 125

2. JavaScript 赋值运算符

我们使用赋值运算符将值赋给变量。例如，

let x = 5;

这里，我们使用 = 运算符将值 5 赋给变量 x。

常用赋值运算符

示例 2：JavaScript 中的赋值运算符

// assignment operator
let a = 7;
console.log("Assignment: a = 7, a =", a);

// addition assignment operator
a += 5;  // a = a + 5
console.log("Addition Assignment: a += 5, a =", a);

// subtraction assignment operator
a -= 5;  // a = a - 5
console.log("Subtraction Assignment: a -= 5, a =", a);

// multiplication assignment operator
a *= 2;  // a = a * 2
console.log("Multiplication Assignment: a *= 2, a =", a);

// division assignment operator
a /= 2;  // a = a / 2
console.log("Division Assignment: a /= 2, a =", a);

// remainder assignment operator
a %= 2;  // a = a % 2
console.log("Remainder Assignment: a %= 2, a =", a);

// exponentiation assignment operator
a **= 2;  // a = a**2
console.log("Exponentiation Assignment: a **= 7, a =", a);

输出

Assignment: a = 7, a = 7
Addition Assignment: a += 5, a = 12
Subtraction Assignment: a -= 5, a = 7
Multiplication Assignment: a *= 2, a = 14
Division Assignment: a /= 2, a = 7
Remainder Assignment: a %= 2, a = 1
Exponentiation Assignment: a **= 7, a = 1

3. JavaScript 比较运算符

我们使用比较运算符来比较两个值并返回一个布尔值（true 或 false）。例如，

const a = 3, b = 2;
console.log(a > b);

// Output: true 

在这里，我们使用 > 比较运算符来检查 a（值为 3）是否大于 b（值为 2）。

因为 3 大于 2，所以我们得到 true 作为输出。

注意：在上面的例子中，a > b 被称为 boolean 表达式，因为它求值后会得到一个 boolean 值。

常用比较运算符

示例 3：JavaScript 中的比较运算符

// equal to operator
console.log("Equal to: 2 == 2 is", 2 == 2);

// not equal operator
console.log("Not equal to: 3 != 3 is", 3 != 3);

// strictly equal to operator
console.log("Strictly equal to: 2 === '2' is", 2 === '2');

// strictly not equal to operator
console.log("Strictly not equal to: 2 !== '2' is", 2 !== '2');

// greater than operator
console.log("Greater than: 3 > 3 is", 3 > 3);

// less than operator
console.log("Less than: 2 > 2 is", 2 > 2);

// greater than or equal to operator
console.log("Greater than or equal to: 3 >= 3 is", 3 >= 3);

// less than or equal to operator
console.log("Less than or equal to: 2 <= 2 is", 2 <= 2);

输出

Equal to: 2 == 2 is true
Not equal to: 3 != 3 is false
Strictly equal to: 2 === '2' is false
Strictly not equal to: 2 !== '2' is true
Greater than: 3 > 3 is false
Less than: 2 > 2 is false
Greater than or equal to: 3 >= 3 is true
Less than or equal to: 2 <= 2 is true

console.log(3 == "3");  // true

console.log(4 === "4");  // false

4. JavaScript 逻辑运算符

我们使用逻辑运算符对布尔表达式执行逻辑运算。例如，

const x = 5, y = 3;
console.log((x < 6) && (y < 5));

// Output: true

这里，&& 是逻辑运算符 AND。由于 x < 6 和 y < 5 都为 true，因此组合结果为 true。

常用逻辑运算符

示例 4：JavaScript 中的逻辑运算符

let x = 3;

// logical AND
console.log((x < 5) && (x > 0));  // true
console.log((x < 5) && (x > 6));  // false

// logical OR
console.log((x > 2) || (x > 5));  // true
console.log((x > 3) || (x < 0));  // false

// logical NOT
console.log(!(x == 3));  // false
console.log(!(x < 2));  // true

注意：我们在决策和循环中使用比较和逻辑运算符。您将在后续教程中详细了解它们。

let str1 = "Hel", str2 = "lo";
console.log(str1 + str2);

// Output: Hello

另请阅读

• JavaScript 扩展运算符
• JavaScript 三元运算符
• JavaScript typeof 运算符