
Software Engineering Radio - the podcast for professional software developers SE Radio 718: Will Sentance on JS Modernization
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Apr 29, 2026 Will Sentance, educator and Codesmith co-founder who teaches advanced JavaScript, explores JavaScript’s growth from a simple script language to the web’s backbone. He discusses backward-compatibility constraints, how community patterns become standards, engine optimizations like monomorphic object shapes, practical coding patterns for performance, and the benefits and risks of LLMs for developer understanding.
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How Flat Replaced Flatten In JavaScript
- The proposed array flatten method became 'flat' after compatibility concerns with MooTools prevented adding 'flatten'.
- Will recounts the 'smoosh gate' debate and how legacy libraries forced a shorter name choice to avoid breaking sites.
Symbols Let You Extend Without Breaking
- Symbols let JavaScript and libraries add properties without colliding with existing names or surprising consumers.
- Symbols are a metaprogramming primitive enabling hidden or opt-in behaviors while preserving old APIs.
Use Community Patterns As Proof Before Standardizing
- Let userland libraries act as R&D: wait until patterns prove essential before standardizing them.
- TC39 treats popular community patterns (e.g., Lodash usage) as a filtration system before adding to the language.

