Error objects: RangeError, TypeError, ValueError

Norbert Lindenberg ecmascript at
Mon Nov 21 17:11:37 PST 2011

At last week's TC39 meeting, I asked which error objects an API should throw when it expects a string matching a specific pattern, but receives a string that doesn't match the pattern. Examples in the Globalization API are language tags, as defined in RFC 5646, or selectors such as "sort" and "search".

Candidates are:

- RangeError - "Indicates a numeric value has exceeded the allowable range." The Language Specification uses it only for that purpose.

- TypeError - "Indicates the actual type of an operand is different than the expected type." Used in the Language Specification not only for differences in "type" as defined in the spec, but also when properties are missing, when objects or properties don't have the attributes needed by an algorithm, or when the [[class]] internal property doesn't have the expected value. The Array.prototype.reduce* functions throw it when a required argument is missing, and the RegExp constructor when an unwanted argument is present. JSON.stringify throws it when given a cyclic structure.

- ValueError - as introduced in the Globalization API spec.

ValueError would be unnecessary if the definition of RangeError or TypeError were expanded to cover string value mismatches as well.

Which way should we go?


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