Later, I saw the ES5 draft history[1], Step 15 in the previous version of the "Sunnyvale"( 23 Feb 2009 ) and step 8.a in the "Sunnyvale"( 02 March 2009 ) are the same intention. Step 15 in the previous version of the "Sunnyvale" is only execute if this number value is 0 and fractionDigits is undefined, But step 8.a in "Sunnyvale" is also execute if fractionDigits is not undefined.
so step 8.a should be "a. if fractionDigits is undefined, then let f = 0.". [1] http://wiki.ecmascript.org/doku.php?id=es3.1:es3.1_proposal_working_draft 在 2012年3月8日 下午10:34，程劭非 <csf...@gmail.com>写道： > I don't think so. > > ES5 specified the algorithm of toExponential. “The number is the same” is > not the only requirement. > > See the algorithm below: ( please pay attention to 8.a ) > > > 1. > > Let *x* be this Number value <http://es5.github.com/#this-Number-value> > . > 2. > > Let *f* be ToInteger <http://es5.github.com/#x9.4>(*fractionDigits*). > 3. > > If *x* is *NaN*, return the String *"NaN"*. > 4. > > Let *s* be the empty String. > 5. > > If *x* *<* 0, then > 1. > > Let *s* be *"-"*. > 2. > > Let *x* = –*x*. > 6. > > If *x* = +∞, then > 1. > > Return the concatenation of the Strings *s* and *"Infinity"*. > 7. > > If *fractionDigits* is not *undefined* and (*f* < 0 or *f* > 20), > throw a *RangeError <http://es5.github.com/#x15.11.6.2>* exception. > 8. > > If *x* = 0, then > 1. > > *Let f = 0.* > 2. > > Let *m* be the String consisting of *f*+1 occurrences of the > character ‘0’. > 3. > > Let *e* = 0. > 9. > > Else, *x* ≠ 0 > 1. > > If fractionDigits is not *undefined*, then > 1. > > Let *e* and *n* be integers such that 10*f* ≤ *n* < 10*f*+1 and > for which the exact mathematical value of *n* × 10*e*–*f* – *x* is > as close to zero as possible. If there are two such sets of *e* > and *n*, pick the *e* and *n* for which *n* × 10*e*–*f* is > larger. > 2. > > Else, *fractionDigits* is *undefined* > 1. > > Let *e*, *n*, and *f* be integers such that *f* ≥ 0, 10*f* ≤ *n* < > 10*f*+1, the number value for n× 10*e*–*f* is *x*, and *f* is as > small as possible. Note that the decimal representation of*n* > has *f*+1 digits, *n* is not divisible by 10, and the least > significant digit of *n* is not necessarily uniquely determined > by these criteria. > 3. > > Let *m* be the String consisting of the digits of the decimal > representation of *n* (in order, with no leading zeroes). > 10. > > If *f* ≠ 0, then > 1. > > Let *a* be the first character of *m*, and let *b* be the remaining > *f* characters of *m*. > 2. > > Let *m* be the concatenation of the three Strings *a*, *"."*, and *b > *. > 11. > > If *e* = 0, then > 1. > > Let *c* = *"+".* > 2. > > Let *d* = *"0".* > 12. > > Else > 1. > > If *e* > 0, then let *c* = *"+".* > 2. > > Else, *e* ≤ 0 > 1. > > Let *c* = *"-"*. > 2. > > Let *e* = –*e*. > 3. > > Let *d* be the String consisting of the digits of the decimal > representation of *e* (in order, with no leading zeroes). > 13. > > Let *m* be the concatenation of the four Strings *m*, *"e"*, *c*, and * > d*. > 14. > > Return the concatenation of the Strings *s* and *m*. > > According to this algorithm, (0).toExponential(1) should return "0e+0".(f > is set to 0) > > But it looks none of V8, spidermonkey and JScript did that thing. Their > result is "0.0e+0". > > So is there anyone could give some message about why does ES5 define this > behavior like this? Or is it simply a spec bug? > > > 2012/3/8 Jens Nockert <j...@nockert.se> > >> >> On H.24/03/08, at 12:39, DX Jin <dox....@gmail.com> wrote: >> >> > (0).toExponential(1) should, according to the algorithm in 15.7.4.6, >> return "0e+0". >> > >> > But all browser implementations return "0.0e+0" instead. >> > >> > Which is wrong? The specification or the implementations? >> >> Neither, the result is correct. The number is the same, just different >> representations as strings. >> _______________________________________________ >> es-discuss mailing list >> es-discuss@mozilla.org >> https://mail.mozilla.org/listinfo/es-discuss >> > > > _______________________________________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/listinfo/es-discuss > >
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