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<meta charset="UTF-8">
<title></title>
<script type="text/javascript">
/*
运算符也叫操作符
通过运算符可以对一个或多个值进行运算
比如:typeof就是运算符,可以来获得一个值的类型
它会将该值的类型以字符串的形式返回
number string boolean undefined object
算术运算符
当对非Number类型的值进行运算时,会将这些值转换为Number在进行计算
+
+可以对两个值进行加法运算,并将结果返回
如果对两个字符串进行加法运算,则会做拼串
会将两个字符串拼接为一个字符串,并返回
任何的值和字符串做加法运算,都会先转换为字符串,然后再和字符串做拼串的操作
-
-可以对两个值进行减法运算,并将结果返回
*
*可以对两个值进行乘法运算
/
/可以对两个值进行除法运算
%
%取模运算(取余数)
*/
var a = 123;
var result = typeof a;
console.log(typeof result);
a + 1;
console.log(a);
a = a + 1;
console.log(a);
a = true + 1;
console.log(a);
a = true + false;
console.log(a);
a = 2 + null;
console.log(a);
a = true + false;
console.log(a);
a = "123" + "456";
console.log(a);
console.log(typeof a);
var str = "锄禾日当午" +
"汗滴禾下土" +
"谁知盘中餐" +
"粒粒皆辛苦";
console.log(str);
a = 123 + "1";
console.log(str);
a = true + "hello";
console.log(str);
//任何值和字符串相加都会转换为字符串,并做拼串操作
a = 123 + "";
// a = String(a);
console.log(typeof a);
console.log(a);
a = null;
a = a + "";
// a = String(a);
console.log(typeof a);
console.log(a);
a = 123;
console.log("a = " + a);
a = 1 + 2 + "3";//33
console.log("a = " + a);
a = "1" + 2 + 3;
console.log("a = " + a);
// 减法运算
a = 100 - 5;
console.log("a = " + a);
a = 100 - true;
console.log("a = " + a);
a = 100 - "1";
console.log("a = " + a);
//乘法运算
a = 2 * 2;
console.log("a = " + a);
a = 2 * "8";
console.log("a = " + a);
a = 2 * undefined;
console.log("a = " + a);
a = 2 * null;
console.log("a = " + a);
// 除法运算
a = 3 / 2;
console.log("a = " + a);
// 任何值做 - * /运算都会自动转换成Number
a = "123";
console.log(typeof a);
console.log("a = " + a);
// a = Number(a);
a = a - 0;
a = a * 1;
a = a / 1;
console.log(typeof a);
console.log("a = " + a);
// 取余运算
a = 9 % 3;
console.log("a = " + a);
</script>
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<!DOCTYPE html>
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<head>
<meta charset="UTF-8">
<title></title>
<script type="text/javascript">
/*
一元运算符,只需要一个操作数
+ 正号
正号不会对数字产生任何影响
- 负号
负号可以对数字进行负号的取反
对于非Number类型的值
它会将其先转换为Number,然后再运算
可以对一个其他的数据类型使用+,将转换为Number
它的原理和Number()一样
*/
var a = 123;
a = +a;
console.log("a = " + a);
a = true;
console.log(typeof a);
console.log(a);
a = -a;
console.log(typeof a);
console.log(a);
a = 18;
console.log(typeof a);
console.log(a);
a = +a;
console.log(typeof a);
console.log(a);
a = 1 + +"2" + 3;
console.log(typeof a);
console.log(a);
</script>
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<body>
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