freeCodeCamp/curriculum/challenges/chinese/02-javascript-algorithms-and-data-structures/basic-javascript/generate-random-whole-numbers-with-javascript.md

id, title, challengeType, videoUrl, forumTopicId, dashedName

id	title	challengeType	videoUrl	forumTopicId	dashedName
cf1111c1c12feddfaeb1bdef	使用 JavaScript 生成随机整数	1	https://scrimba.com/c/cRn6bfr	18186	generate-random-whole-numbers-with-javascript

--description--

You can generate random decimal numbers with Math.random(), but sometimes you need to generate random whole numbers. The following process will give you a random whole number less than 20:

1. Use Math.random() to generate a random decimal number.
2. Multiply that random decimal number by 20.
3. Use Math.floor() to round this number down to its nearest whole number.

Remember that Math.random() can never quite return a 1, so it's impossible to actually get 20 since you are rounding down with Math.floor(). This process will give you a random whole number in the range from 0 to 19.

Putting everything together, this is what your code looks like:

Math.floor(Math.random() * 20);

You are calling Math.random(), multiplying the result by 20, then passing the value to Math.floor() to round the value down to the nearest whole number.

--instructions--

Use this technique to generate and return a random whole number in the range from 0 to 9.

--hints--

randomWholeNum 的结果应该是一个整数。

assert(
  typeof randomWholeNum() === 'number' &&
    (function () {
      var r = randomWholeNum();
      return Math.floor(r) === r;
    })()
);

应该使用 Math.random 生成一个随机数字。

assert(code.match(/Math.random/g).length >= 1);

You should have multiplied the result of Math.random by 10 to make it a number in the range from zero to nine.

assert(
  code.match(/\s*?Math.random\s*?\(\s*?\)\s*?\*\s*?10[\D]\s*?/g) ||
    code.match(/\s*?10\s*?\*\s*?Math.random\s*?\(\s*?\)\s*?/g)
);

应该使用 Math.floor 来删除数字的十进制部分。

assert(code.match(/Math.floor/g).length >= 1);

--seed--

--after-user-code--

(function(){return randomWholeNum();})();

--seed-contents--

function randomWholeNum() {
  return Math.random();
}

--solutions--

function randomWholeNum() {
  return Math.floor(Math.random() * 10);
}