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What is the motivation for the Date.prototype.toString() non-Date receiver support? #849

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littledan opened this Issue Mar 17, 2017 · 0 comments

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littledan commented Mar 17, 2017

In the spec, Date.prototype.toString falls back to "Invalid Date" when the receiver is a non-Date Object. However, apparently d8 and jsc don't implement this and throw a TypeError, both for Date.prototype and for {}. ChakraCore seems to return "Invalid Date" for Date.prototype and throw for other objects, and SpiderMonkey implements the spec properly.

What was the motivation for this path in Date.prototype.toString? Was it web compatibility? If so, it seems like we have some evidence that it could be removed. It looks like this path wasn't present in the ES 5.1 version.

@littledan littledan added question web reality labels Mar 17, 2017

littledan added a commit to littledan/ecma262 that referenced this issue Mar 18, 2017

@littledan
Normative: Date.prototype.toString throws on non-Date receiver 
JSC and V8 have been shipping the version of the specification
included in this patch, so it is likely to be web-compatible.
Throwing on receivers which are not Date instances is simpler
and more consistent with other methods in ECMAScript.

Closes tc39#849
c52acbf

@littledan littledan referenced this issue Mar 18, 2017

Merged

Normative: Date.prototype.toString throws on non-Date receiver #850

littledan added a commit to littledan/test262 that referenced this issue Mar 21, 2017

@littledan
Test that Date.prototype.toString throws for non-Date receiver 
Pending discussion of tc39/ecma262#849

Test passes in V8.
7151f32

@littledan littledan referenced this issue Mar 21, 2017

Merged

Test that Date.prototype.toString throws for non-Date receiver #924

littledan added a commit to littledan/test262 that referenced this issue Mar 23, 2017

@littledan
Test that Date.prototype.toString throws for non-Date receiver 
Pending discussion of tc39/ecma262#849

Test passes in V8.
e0b71ae

@bterlson bterlson closed this in #850 Jun 28, 2017

bterlson added a commit that referenced this issue Jun 28, 2017

@littledan @bterlson
Normative: Date.prototype.toString throws on non-Date receiver (#850) 
JSC and V8 have been shipping the version of the specification
included in this patch, so it is likely to be web-compatible.
Throwing on receivers which are not Date instances is simpler
and more consistent with other methods in ECMAScript.

Closes #849
0264be5
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