• +
• -
• *
• /
• %

## 算术运算符的优先级和结合性

* / % 的优先级要高于 + -，无论是 + - * / %都是左结合性(从左至右计算)

## 加

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title>Demo</title>    <script>        let resultOne = 1 + 1;        console.log(resultOne);        let num1, num2;        num1 = 3;        num2 = 5;        let resultTwo = num1 + num2;        console.log(resultTwo);        let resultThree = num1 + 3;        console.log(resultThree);    </script></head><body></body></html>

## 减

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title>Demo</title>    <script>        let resultOne = 2 - 1;        console.log(resultOne);        let numOne, numTwo;        numOne = 3;        numTwo = 9;        let resultTwo = numOne - numTwo;        console.log(resultTwo);    </script></head><body></body></html>

## 乘

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title>Demo</title>    <script>        let result = 1 + 2 * 5;                console.log(result);    </script></head><body></body></html>

## 除

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title>Demo</title>    <script>        let result = 1 / 3;        console.log(result);    </script></head><body></body></html>

## 取余

<!DOCTYPE html><html lang="en"><head>    <meta charset="UTF-8">    <title>Demo</title>    <script>        /*        被除数  除数   商  余数        10   ÷ 3   =  3   1        */        let result = 10 % 3;        console.log(result);    </script></head><body></body></html>