1、运算符介绍

取一个简单的表达式2 + 3 = 5。这里2和3被称为操作数，而"+"被称为操作符。JavaScript支持以下类型的操作符。

• 算术运算符
• 比较运算符
• 逻辑(或关系)操作符
• 赋值操作符
• 条件(或三元)操作符

2、算术运算符

JavaScript支持以下算术运算符

假设变量x为10，变量y为20。

注意：加法运算符(+)适用于数字和字符串。如。“a”+ 10 等于 “a10”。

在JavaScript中使用算术运算符，例如，

var a = 33;
var b = 10;
var c = "Test";
var linebreak = "\n";
console.log("a + b = ");
result = a + b;
console.log(result);
console.log(linebreak);
console.log("a - b = ");
result = a - b;
console.log(result);
console.log(linebreak);
console.log("a / b = ");
result = a / b;
console.log(result);
console.log(linebreak);
console.log("a % b = ");
result = a % b;
console.log(result);
console.log(linebreak);
console.log("a + b + c = ");
result = a + b + c;
console.log(result);
console.log(linebreak);
a = ++a;
console.log("++a = ");
result = ++a;
console.log(result);
console.log(linebreak);
b = --b;
console.log("--b = ");
result = --b;
console.log(result);
console.log(linebreak);

将变量设置为不同的值，尝试查看效果。

3、比较运算符

JavaScript支持以下比较操作符：

假设x值为5，y值为6

在JavaScript中使用比较运算符，例如，

var a = 10;
var b = 20;
var linebreak = "\n";
console.log("(a == b) => ");
result = (a == b);
console.log(result);
console.log(linebreak);
console.log("(a < b) => ");
result = (a < b);
console.log(result);
console.log(linebreak);
console.log("(a > b) => ");
result = (a > b);
console.log(result);
console.log(linebreak);
console.log("(a != b) => ");
result = (a != b);
console.log(result);
console.log(linebreak);
console.log("(a >= b) => ");
result = (a >= b);
console.log(result);
console.log(linebreak);
console.log("(a <= b) => ");
result = (a <= b);
console.log(result);
console.log(linebreak);

4、逻辑运算符

JavaScript支持以下逻辑运算符。

假设x值为5，y值为6 。

在 JavaScript 中实现逻辑运算符。例如，

var a = true;
var b = false;
var linebreak = "\n";
console.log("(a && b) => ");
result = (a && b);
console.log(result);
console.log(linebreak);
console.log("(a || b) => ");
result = (a || b);
console.log(result);
console.log(linebreak);
console.log("!(a && b) => ");
result = (!(a && b));
console.log(result);
console.log(linebreak);

5、位运算符

JavaScript 支持以下按位运算符 。

假设变量 x 为 2，变量 y 为 3，

在 JavaScript 中实现按位运算符，例如，

var a = 2; // Bit presentation 10
var b = 3; // Bit presentation 11
var linebreak = "\n";
console.log("(a & b) => ");
result = (a & b);
console.log(result);
console.log(linebreak);
console.log("(a | b) => ");
result = (a | b);
console.log(result);
console.log(linebreak);
console.log("(a ^ b) => ");
result = (a ^ b);
console.log(result);
console.log(linebreak);
console.log("(~b) => ");
result = (~b);
console.log(result);
console.log(linebreak);
console.log("(a << b) => ");
result = (a << b);
console.log(result);
console.log(linebreak);
console.log("(a >> b) => ");
result = (a >> b);
console.log(result);
console.log(linebreak);

6、赋值运算符

JavaScript 支持以下赋值运算符。

注意：同样的逻辑也适用于位操作符，因此它们将变成<<=、>>=、>>=、&=、|=和^=。

在 JavaScript 中实现赋值运算符。例如，

var a = 33;
var b = 10;
var linebreak = "\n";
console.log("Value of a => (a = b) => ");
result = (a = b);
console.log(result);
console.log(linebreak);
console.log("Value of a => (a += b) => ");
result = (a += b);
console.log(result);
console.log(linebreak);
console.log("Value of a => (a -= b) => ");
result = (a -= b);
console.log(result);
console.log(linebreak);
console.log("Value of a => (a *= b) => ");
result = (a *= b);
console.log(result);
console.log(linebreak);
console.log("Value of a => (a /= b) => ");
result = (a /= b);
console.log(result);
console.log(linebreak);
console.log("Value of a => (a %= b) => ");
result = (a %= b);
console.log(result);
console.log(linebreak);

7、其它运算符

两个在 JavaScript 中非常有用的运算符：条件运算符(?:) 和typeof 运算符。

条件运算符 (? :)

条件运算符首先计算表达式的真值或假值，然后根据计算结果执行两个给定语句之一。

了解条件运算符在 JavaScript 中的工作原理。例如，

var a = 10;
var b = 20;
var linebreak = "\n";
console.log ("((a > b) ? 100 : 200) => ");
result = (a > b) ? 100 : 200;
console.log(result);
console.log(linebreak);
console.log ("((a < b) ? 100 : 200) => ");
result = (a < b) ? 100 : 200;
console.log(result);
console.log(linebreak);

运算符类型

typeof运算操作是一元运算符是其单个操作数之前放置，其可以是任何类型的。它的值是一个字符串，指示操作数的数据类型。

typeof运算符的返回值列表。

实现typeof运算符。例如，

var a = 10;
var b = "String";
var linebreak = "\n";
result = (typeof b == "string" ? "B is String" : "B is Numeric");
console.log("Result => ");
console.log(result);
console.log(linebreak);
result = (typeof a == "string" ? "A is String" : "A is Numeric");
console.log("Result => ");
console.log(result);
console.log(linebreak);