--- title: "Implementing Iterator.range in SpiderMonkey" url: https://daily.dev/posts/implementing-iterator-range-in-spidermonkey-efwxbwspi source_url: https://spidermonkey.dev/blog/2025/03/05/iterator-range.html type: article source: "SpiderMonkey" published: 2025-03-05T15:46:57.464Z updated: 2025-03-05T15:47:12.531Z tags: ["javascript", "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 Serah Nderi shares her experience implementing the TC39 Range Proposal in the SpiderMonkey JavaScript engine. Iterator.range allows generating a sequence of numbers within a specified range, similar to Python’s range. Initially implemented with a generator-based approach, it was later optimized to a slot-based approach resulting in a 66.7% performance improvement. Challenges included handling Infinity checks and floating-point precision errors. The proposal is currently at stage 1 and built in Nightly only, disabled by default until it advances to further stages. ## 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), [#webassembly](https://daily.dev/tags/webassembly) [View this post on daily.dev](https://daily.dev/posts/implementing-iterator-range-in-spidermonkey-efwxbwspi)