Maximum String length
Claude Pache
claude.pache at gmail.com
Wed Jan 28 04:14:44 PST 2015
> Le 28 janv. 2015 à 09:58, Jordan Harband <ljharb at gmail.com> a écrit :
>
> Typically, implementation-specific things aren't specified in the spec (like Math precision, etc) - although usually when it's implementation-specific, it's explicitly noted as such ( https://people.mozilla.org/~jorendorff/es6-draft.html#sec-date.parse <https://people.mozilla.org/~jorendorff/es6-draft.html#sec-date.parse> , https://people.mozilla.org/~jorendorff/es6-draft.html#sec-math.hypot <https://people.mozilla.org/~jorendorff/es6-draft.html#sec-math.hypot> , https://people.mozilla.org/~jorendorff/es6-draft.html#sec-ecmascript-language-types-number-type <https://people.mozilla.org/~jorendorff/es6-draft.html#sec-ecmascript-language-types-number-type> , https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object.keys <https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object.keys> , etc)
>
> Strings are only defined in ES6 as a "primitive value that is a finite ordered sequence of zero or more 16-bit unsigned integer" ( https://people.mozilla.org/~jorendorff/es6-draft.html#sec-terms-and-definitions-string-value <https://people.mozilla.org/~jorendorff/es6-draft.html#sec-terms-and-definitions-string-value> ) and are not noted as having any implementation-specific or implementation-dependent qualities.
>
> To me, "finite" here means `Number.MAX_VALUE` - ie, the highest number I can get before I reach Infinity. An alternative reading is "any number greater than zero that's not Infinity" - but at that point an implementation conforms if it's max length is 1, which obviously would be silly.
>
To me, "finite" is just to be taken in the common mathematical sense of the term; in particular you could have theoretically a string of length 10^10000. But yes, it would be reasonable to restrict oneself to strings of length at most 2^52, so that `string.length` could always return an exact answer.
—Claude
> However, Chrome 40 and Opera 26-27 have a limit of `0xFFFFFF0` (`2**28 - 2**4`), Firefox 35 and IE 9-11 all have a limit of `0xFFFFFFF` (`2**28 - 1`), and Safari 8 has `0x7FFFFFFF` (`2**31 - 1`). There's many more browsers I haven't tested of course but it'd be interesting to know how wide these numbers deviate.
>
> 1) Should an engine's max string length be exposed, like `Number.MAX_VALUE`, as `String.MAX_LENGTH`? This will help, for example, my `String#repeat` polyfill throw an earlier `RangeError` rather than having to try to build a string of that length.
> 2) Should the spec require a minimum maximum string length, or at least be more specific in how it defines "finite"?
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