JavaScript 随机


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Math.random()

Math.random() 返回 0(含)和 1 之间的随机数 (独家的):

例子

// Returns a random number:
Math.random();

自己尝试一下 →

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math.random()</h2>

<p>Math.random() returns a random number between 0 (included) and 1 (excluded):</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML = Math.random();
</script>

</body>
</html>

Math.random() 始终返回小于 1 的数字。


JavaScript 随机整数

Math.floor() 一起使用的 Math.random() 可用于返回随机整数。

JavaScript 中不存在整数这样的东西。

我们在这里讨论的是没有小数的数字。

例子

// Returns a random integer from 0 to 9:
Math.floor(Math.random() * 10);

自己尝试一下 →

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math</h2>

<p>Math.floor(Math.random() * 10) returns a random integer between 0 and 9 (both 
included):</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML =
Math.floor(Math.random() * 10);
</script>

</body>
</html>

例子

// Returns a random integer from 0 to 10:
Math.floor(Math.random() * 11);

自己尝试一下 →

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math</h2>

<p>Math.floor(Math.random() * 11) returns a random integer between 0 and 10 (both included):</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML =
Math.floor(Math.random() * 11);
</script>

</body>
</html>

例子

// Returns a random integer from 0 to 99:
Math.floor(Math.random() * 100);

自己尝试一下→

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math</h2>

<p>Math.floor(Math.random() * 100)) returns a random integer between 0 and 99 
(both included):</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML =
Math.floor(Math.random() * 100);
</script>

</body>
</html>

例子

// Returns a random integer from 0 to 100:
Math.floor(Math.random() * 101);

自己尝试一下→

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math</h2>

<p>Math.floor() used with Math.random() * 101 returns a random integer between 0 and 100 
(both included):</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML =
Math.floor(Math.random() * 101);
</script>

</body>
</html>

例子

// Returns a random integer from 1 to 10:
Math.floor(Math.random() * 10) + 1;

自己尝试一下→

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math</h2>

<p>Math.floor(Math.random() * 10) + 1) returns a random integer between 1 and 10 
(both included):</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML =
Math.floor(Math.random() * 10) + 1;
</script>

</body>
</html>

例子

// Returns a random integer from 1 to 100:
Math.floor(Math.random() * 100) + 1;

自己尝试一下→

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math</h2>

<p>Math.floor(Math.random() * 100) + 1) returns a random integer between 1 and 
100 (both included):</p>

<p id="demo"></p>

<script>
document.getElementById("demo").innerHTML =
Math.floor(Math.random() * 100) + 1;
</script>

</body>
</html>


适当的随机函数

正如您从上面的示例中看到的,创建适当的随机函数可能是个好主意 用于所有随机整数目的。

此 JavaScript 函数始终返回 min(包括)和 min 之间的随机数 最大(不包括):

例子

function getRndInteger(min, max) {
  return Math.floor(Math.random() * (max - min) ) + min;
}

自己尝试一下→

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math.random()</h2>

<p>Every time you click the button, getRndInteger(min, max) returns a random number between 0 
and 9 (both included):</p>

<button onclick="document.getElementById('demo').innerHTML = getRndInteger(0,10)">Click Me</button>

<p id="demo"></p>

<script>
function getRndInteger(min, max) {
  return Math.floor(Math.random() * (max - min)) + min;
}
</script>

</body>
</html>

这个 JavaScript 函数总是返回一个介于 min 和 max 之间的随机数(包括两者):

例子

function getRndInteger(min, max) {
    return Math.floor(Math.random() * (max - min + 1) ) + min;
}

自己尝试一下→

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Math.random()</h2>

<p>Every time you click the button, getRndInteger(min, max) returns a random number between 1 and 10 (both included):</p>

<button onclick="document.getElementById('demo').innerHTML = getRndInteger(1,10)">Click Me</button>

<p id="demo"></p>

<script>
function getRndInteger(min, max) {
  return Math.floor(Math.random() * (max - min + 1) ) + min;
}
</script>

</body>
</html>