The semantics of a programming language isn't determined by how you talk about it or even how the language specification talks about it.

The original statement was: "(I program in JavaScript where all values are immutable)" Its meaning depends on the semantics of 'values' and 'immutable'. If by 'values' you only mean primitive values (excluding objects and arrays) or by immutable you only mean immutable identity (excluding mutable state), you're comparing apples to oranges instead of Rust to JavaScript.

Immutable.js and PureScript exists for a reason: in JavaScript, not all values are immutable.