Ruby's Array.sample in JavaScript

How to use

You you can install via yarn add locutus and require this function via const sample = require('locutus/ruby/Array/sample').

It is important to use a bundler that supports tree-shaking so that you only ship the functions that you actually use to your browser, instead of all of Locutus, which is massive. Examples are: Parcel, webpack, or rollup.js. For server-side use this is typically less of a concern.

Examples

Please note that these examples are distilled from test cases that automatically verify our functions still work correctly. This could explain some quirky ones.

#	code	expected result
1	[1, 2, 3].indexOf(sample([1, 2, 3])) !== -1	true
2	sample([1, 2, 3], 2).length	2

Ruby nil and JavaScript undefined

Ruby's nil and JavaScript's undefined are semantically equivalent—both represent "no value" or "nothing here". However, they serialize differently: nil becomes null in JSON, while undefined is typically omitted or becomes undefined.

Locutus Ruby functions return undefined (idiomatic JavaScript) where Ruby would return nil. Our parity tests treat these as equivalent when verifying against native Ruby.

Notes

• Returns a random element, or n random elements, from the array. Uses Math.random() for randomness.

Here's what our current JavaScript equivalent to Ruby's Array.sample looks like.

module.exports = function sample(arr, n) {
  //  discuss at: https://locutus.io/ruby/Array/sample/
  // original by: Kevin van Zonneveld (https://kvz.io)
  //      note 1: Returns a random element, or n random elements, from the array.
  //      note 1: Uses Math.random() for randomness.
  //   example 1: [1, 2, 3].indexOf(sample([1, 2, 3])) !== -1
  //   returns 1: true
  //   example 2: sample([1, 2, 3], 2).length
  //   returns 2: 2

  if (!Array.isArray(arr) || arr.length === 0) {
    return n === undefined ? undefined : []
  }

  if (n === undefined) {
    return arr[Math.floor(Math.random() * arr.length)]
  }

  // Fisher-Yates shuffle for selecting n unique elements
  const copy = arr.slice()
  const result = []
  const count = Math.min(n, copy.length)

  for (let i = 0; i < count; i++) {
    const idx = Math.floor(Math.random() * copy.length)
    result.push(copy[idx])
    copy.splice(idx, 1)
  }

  return result
}

Think you can do better?

Not unlike Wikipedia, Locutus is an ongoing community effort. Our philosophy follows The McDonald’s Theory. This means that we assimilate first iterations with imperfections, hoping for others to take issue with-and improve them. This unorthodox approach has worked very well to foster fun and fruitful collaboration, but please be reminded to use our creations at your own risk. THE SOFTWARE IS PROVIDED "AS IS" has never been more true than for Locutus.

Now go and: [ View on GitHub | Edit on GitHub | View Raw ]

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Ehm.. only 32 Ruby functions?

We can use your help porting more. Have a rainy Sunday afternoon to spare and a taste for a porting puzzle?

• Get inspiration from the Ruby core documentation.
• Click "New file" in the appropriate folder on GitHub. This will fork the project to your account, directly add the file to it, and send a Pull Request to us.

We will then review it. If it's useful to the project and in line with our contributing guidelines your work will become part of Locutus and you'll be automatically credited in the authors section accordingly.

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