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JavaScript-Math内置对象

向下取整

Math.floor():向下取整直接砍掉所有的小数位就是向下取整:

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Demo</title>
<script>
let num = 3.9;
let value = Math.floor(num);
console.log(value);
</script>
</head>
<body>
</body>
</html>

向上取整

Math.ceil():向上取整只要有小数位就会给整数位 ​​+1​​,然后砍掉所有小数位:

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Demo</title>
<script>
let num = 3.9;
let value = Math.ceil(num);
console.log(value);
</script>
</head>
<body>
</body>
</html>

四舍五入

Math.round():四舍五入和小学数学一样,如果小数位满 5 就会进 1:

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Demo</title>
<script>
let num = 3.5;
let value = Math.round(num);
console.log(value);
</script>
</head>
<body>
</body>
</html>

绝对值

Math.abs():和小学数学一样,统一变为正数:

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

生成随机数

Math.random():生成随机数,会生成一个 ​​0~1​​ 的随机数,但是不包括1:

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

需求:要求生成一个 ​​1~10​​ 的随机数:

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Demo</title>
<script>
function getRandomIntInclusive(min, max) {
min = Math.ceil(min);
max = Math.floor(max);
// 含最大值,含最小值
return Math.floor(Math.random() * (max - min + 1)) + min;
}

let value = getRandomIntInclusive(1, 10);
console.log(value);
</script>
</head>
<body>
</body>
</html>





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