ES6 doesn't need opt-in

Brendan Eich brendan at mozilla.com
Sat Jan 7 20:39:23 PST 2012


On Jan 7, 2012, at 8:00 PM, Gavin Barraclough wrote:

> Would the implicit opt-in proposal not mean that any programmer wanting to pick up JavaScript would need to learn the history of when different syntactic constructs came into the language specification in order to understand the semantics that a given script would be evaluated with?

If there's new syntax somewhere, the consumer of the code may have to read and understand it. But let's be real: JQuery users *do not* read and understand that library's every line. They use its well-documented APIs.

Remember, we are not proposing breaking semantic shifts of meaning for existing syntax. So the realistic worry is that you have code with arguments[i] aliasing a formal, and this is required for correct operation, and you then start using ES6 features (which imply ES5-strict), which breaks arguments aliasing.

/be



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