Fix corner-case issues identified in testing #10
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jessealama
reviewed
Oct 30, 2025
| 1. If _x_ is not ~negative-zero~, then | ||
| 1. Assert: _x_ is a mathematical value. | ||
| 1. If _numberFormat_.[[Style]] is *"percent"*, set _x_ be 100 × _x_. | ||
| 1. <ins>Let _magnitude_ be the base 10 logarithm of abs(_x_) rounded down to the nearest integer.</ins> |
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While putting together tc39/test262#4608, I validated the proposed spec text with a patched fork of FormatJS, and this identified a few places where the spec text needs to be updated:
Leading zeros need to be discarded, so we count
'0012.3'to have three string digits. To do so in the syntax-directed operation, I introduceZeroDigitsas a new syntax rule.An elided leading zero needs to be accounted for, so
'.45'should count as having three string digits.Changes in exponents that reduce the number of leading zeros need to also reduce the string digit count accordingly. This means that when formatted as a percentage,
'0.06'should format as if it had only one string digit, rather than three. This adjustment needs to be done potentially twice, asstyle: 'percent'can be combined withnotation: 'engineering'ornotation: 'scientific'.Ping @sffc, @gibson042, @jessealama, @ben-allen for reviews.