Formally introduce sparse arrays

[Josh-Cena]

Summary

Motivation

Fix #14441. I've also fixed a few places where we confuse "empty slots" with undefined.

Supporting details

Related issues

Metadata

• Adds a new document
• Rewrites (or significantly expands) a document
• Fixes a typo, bug, or other error

[github-actions]

Preview URLs

• https://pr16326.content.dev.mdn.mozit.cloud/en-US/docs/Web/JavaScript/Guide/Grammar_and_types
• https://pr16326.content.dev.mdn.mozit.cloud/en-US/docs/Web/JavaScript/Guide/Indexed_collections
• https://pr16326.content.dev.mdn.mozit.cloud/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Array
• https://pr16326.content.dev.mdn.mozit.cloud/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/length

Flaws

None! 🎉

External URLs

URL: /en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/length
Title: Array.prototype.length
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Array
Title: Array() constructor
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/JavaScript/Guide/Indexed_collections
Title: Indexed collections
on GitHub

No new external URLs

---

URL: /en-US/docs/Web/JavaScript/Guide/Grammar_and_types
Title: Grammar and types
on GitHub

No new external URLs

(this comment was updated 2022-05-22 08:14:58.649678)

[teoli2003]

Thank you!