如何随机生成-​​0.5到0.5范围内的数字? [英] How can I randomly generate a number in the range -0.5 and 0.5?

问题描述

在javascript中，我如何随机生成-​​0.5到0.5之间的数字?以下似乎只给出了正数，而没有给出负数.

In javascript how do I randomly generate a number between -0.5 and 0.5? The following only seems to give positive numbers, and no negative numbers.

Math.random(-0.15, 0.15)

推荐答案

在

Math.random()函数返回浮点伪随机数，范围为[0，1)，范围从0(包括0)到但不包括1(独家)

The Math.random() function returns a floating-point, pseudo-random number in the range [0, 1) that is, from 0 (inclusive) up to but not including 1 (exclusive)

因此，生成0到1之间的随机数，并从中减去0.5.

So, generate random numbers between 0 and 1 and subtract 0.5 from it.

Math.random() - 0.5

注意: Math.random()不需要任何参数.因此，您不能指定任何范围.

Note: Math.random() doesn't expect any parameters. So, you cannot specify any range.

如果要在一个范围之间生成随机数，请使用

If you want to generate random numbers between a range, use the example snippets in MDN,

// Returns a random number between min (inclusive) and max (exclusive)
function getRandomArbitrary(min, max) {
  return Math.random() * (max - min) + min;
}

---

具有范围的演示

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


function appendToResult(value) {
  document.getElementById("result").innerHTML += value + "<br />";
}

document.getElementById("result").innerHTML = "";

for (var i = 0; i < 10; i += 1) {
  appendToResult(getRandomArbitrary(-0.35, 0.35));
}

<pre id="result" />

之所以有效，是因为表达式

This works because, the expression

Math.random() * (max - min) + min

将以以下方式进行评估.首先，

will be evaluated in the following manner. First,

Math.random()

将被评估为获得0到1之间的随机数，然后

will be evaluated to get a random number in the range 0 and 1 and then

Math.random() * (max - min)

它将乘以 max 和 min 值之间的差.在您的情况下，假设 max 是 0.35 ，而 min 是 -0.35 .因此， max-min 变为 0.7 .因此， Math.random()*(max-min)给出一个在 0 和 0.7 范围内的数字(因为即使Math.random()生成 1 ，将其与 0.7 相乘，结果将变为 0.7 .).然后，你做

it will be multiplied with the difference between max and min value. In your case, lets say max is 0.35 and min is -0.35. So, max - min becomes 0.7. So, Math.random() * (max - min) gives a number in the range 0 and 0.7 (because even if Math.random() produces 1, when you multiply it with 0.7, the result will become 0.7). Then, you do

Math.random() * (max - min) + min

所以，就您的情况而言，基本上变成了

So, for your case, that basically becomes,

Math.random() * (0.35 - (-0.35)) + (-0.35)
(Math.random() * 0.7) - 0.35

因此，如果(Math.random()* 0.7)生成任何大于 0.35 的值，因为您从中减去了 0.35 ，它变成介于 0 和 0.35 之间的某个数字.如果(Math.random()* 0.7)生成的值小于 0.35 ，则由于您从中减去了 0.35 ，因此它成为一个介于 -0.35 和 0 .

So, if (Math.random() * 0.7) generates any value greater than 0.35, since you subtract 0.35 from it, it becomes some number between 0 and 0.35. If (Math.random() * 0.7) generates a value lesser than 0.35, since you subtract 0.35 from it, it becomes a number between -0.35 and 0.

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