--- title: "Implementing Iterator.range in SpiderMonkey" url: https://daily.dev/posts/implementing-iterator-range-in-spidermonkey-lfp5vzuh5 source_url: https://spidermonkey.dev/blog/2025/02/26/iterator-range.html type: article source: "SpiderMonkey" published: 2025-03-05T15:16:54.379Z updated: 2025-03-05T15:17:08.724Z tags: ["javascript", "open-source", "webassembly"] reading_time: 7 upvotes: 0 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Implementing Iterator.range in SpiderMonkey **[SpiderMonkey](https://daily.dev/sources/spidermonkey)** · 7 min read · 0 upvotes · 0 comments ## Summary In October 2024, the author joined Outreachy and later interned with Mozilla, tasked with implementing the TC39 Range Proposal in the SpiderMonkey JavaScript engine. The new Iterator.range method generates sequences of numbers within a specified range, akin to Python's range. Initially implemented with generators, the approach shifted to a more efficient slot-based method, leading to significant performance improvements. Key challenges included addressing precision errors and handling infinity checks. The proposal is currently in its early stages, built in Nightly and disabled by default until advanced stages of TC39 approval are reached. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Don’t just attend KubeCon \+ CloudNativeCon, Merge Forward your experience\!](https://daily.dev/posts/don-t-just-attend-kubecon-cloudnativecon-merge-forward-your-experience--l0rpp73x8) · CNCF · 0 upvotes · 0 comments - [Announcing H2 2026 KCDs](https://daily.dev/posts/announcing-h2-2026-kcds-m96goajm1) · CNCF · 1 upvotes · 0 comments - [Two months of Open Community Groups](https://daily.dev/posts/two-months-of-open-community-groups-asf52zhbs) · CNCF · 0 upvotes · 0 comments --- Tags: [#javascript](https://daily.dev/tags/javascript), [#open-source](https://daily.dev/tags/open-source), [#webassembly](https://daily.dev/tags/webassembly) [View this post on daily.dev](https://daily.dev/posts/implementing-iterator-range-in-spidermonkey-lfp5vzuh5)