1、Math
- Math is a built-in object, it has some mathematical constant properties and mathematical function methods, Math is not a function object
————— quoted from the official website
2. Description
- Unlike other global objects, Math is not a constructor. All properties and methods of Math are static. The way to quote pi is Math.PI, and the way to call the sine and cosine function is Math.sin(x), where x is the parameter to be passed in. Math constants are defined using full-precision floating-point numbers in JavaScript.
————— Quoted from the official website
3. Method
(1) Obtain random numbers
- The random number returns a number between 0 and 1 by default
① Syntax format:
Math.random();
② Example:
//这里为了方便展示效果，用for循环输出10次随机数
<script>
let Num;
for (i = 1;i <= 10;i++){
Num = Math.random();
console.log(Num);
}
</script>
③ Operation effect
(2) Obtain an integer random number
Method 1 (rounding)
- parseInt(Math.random()*(maximum-minimum+1))+minimum
Method 2 (round down)
- Math.floor(Math.random()*(maximum-minimum+1))+minimum
① Syntax format:
- Get a random number from 1 to 10
//取整
parseInt(Math.random() * (最大值 - 最小值 + 1 )) + 最小值;
//向下取整
Math.floor(Math.random() * (最大值 - 最小值 + 1)) + 最小值;
② Example:
//取整，用for循环取10次随机数
<script>
let Num;
for (i = 1;i <= 10;i++){
//公式：parseInt(Math.random() * (最大值 - 最小值 + 1)) + 最小值
Num = parseInt(Math.random() * (10 - 1 + 1)) + 1;
//最小值为1的时候可以简写：Num = parseInt(Math.random() * 10) + 1
document.write(Num + ' ');
}
</script>
running result
//向下取整，用for循环取10次随机数
<script>
let Num;
for (i = 1;i <= 10;i++){
//公式：Math.floor(Math.random() * (最大值 - 最小值 + 1)) + 最小值;
Num = Math.floor(Math.random() * (10 - 1 + 1)) + 1;
//最小值为1的时候可以简写：Num = parseInt(Math.random() * 10) + 1
document.write(Num + ' ');
}
</script>
running result
(3) Rounding
① Syntax format:
Math.round();
② Example:
<script>
let NumOne = Math.round(7.56);
let NumTwo = Math.round(7.05);
document.write(`
7.56四舍五入等于：${
NumOne} <br />
7.05四舍五入等于：${
NumTwo}
`);
// <br />：换行
</script>
③ Operation effect
(4) Round down
① Syntax format:
Math.floor();
② Example:
<script>
let NumOne = Math.floor(7.55);
let NumTwo = Math.floor(7.05);
document.write(`
7.55向下取整等于：${
NumOne} <br />
7.05向下取整等于：${
NumTwo}
`);
// <br />：换行
</script>
③ Operation effect
(5) Round up
① Syntax format:
Math.ceil();
② Example:
<script>
let NumOne = Math.ceil(7.55);
let NumTwo = Math.ceil(7.05);
document.write(`
7.55向上取整等于：${
NumOne} <br />
7.05向上取整等于：${
NumTwo}
`);
// <br />：换行
</script>
③ Operation effect
(6) power
① Syntax format:
Math.pow(底数,指数/幂);
② Example:
<script>
//计算2的三次方
let NumOne = Math.pow(2,3);
//计算3的三次方
let NumTwo = Math.pow(3,3);
document.write(`
2的三次方等于：${
NumOne} <br />
3的三次方等于：${
NumTwo}
`)
</script>
③ Operation effect
(7) Absolute value
① Syntax format:
Math.abs();
② Example:
<script>
let NumOne = Math.abs(-100);
let NumTwo = Math.abs(-200);
document.write(`
-100的绝对值等于：${
NumOne} <br />
-200的绝对值等于：${
NumTwo}
`)
</script>
③ Operation effect
(8) Square root
① Syntax format:
Math.sqrt();
② Example:
<script>
let NumOne = Math.sqrt(9);
let NumTwo = Math.sqrt(25);
let NumThr = Math.sqrt(81);
document.write(`
9的平方根等于：${
NumOne} <br />
25的平方根等于：${
NumTwo} <br />
81的平方根等于：${
NumThr}
`)
</script>
③ Operation effect
(9) Maximum/minimum value
① Syntax format:
//最大值
Math.max();
//最小值
Math.min();
② Example:
<script>
let NumMax = Math.max(1,11,111,1111,11111);
let NumMin = Math.min(1,11,111,1111,11111);
document.write(`
最大值为：${
NumMax} <br />
最小值为：${
NumMin}
`)
</script>
③ Operation effect
For more mathematical object learning, please refer to the official document
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Math