@@toStringTag spoofing for null and undefined

Allen Wirfs-Brock allen at wirfs-brock.com
Wed Feb 11 08:30:12 PST 2015

TC39 members were aware that changing to using ordinary objects as the prototypes of the legacy built-ins was a breaking change (for example, it changes the prototypes {}.toString value). What we agreed to do was to make that change but to undo it for individual legacy built-ins if we discovered that it would cause actual significant web breakage.  We discovered that this was the case for Function.prototype and so it remains a function instances in the ES6 spec

What we need for the other legacy built-ins is real evidence that there is a problem, rather than speculation. Let us know if you are aware of a significant Web site or widely used framework that depends upon String.prototype being a String instance  or any other similar dependency.


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