last link is [the test file]( https://github.com/WebReflection/define-strict-properties/blob/master/test/define-strict-properties.js) which better than examples in here describes what happens when the library is around, how ES5 descriptors can guard properties and methods within objects or prototypal inheritance.
I hope what is this about is a bit more clear. Best Regards On Sun, Mar 9, 2014 at 2:30 PM, Andrea Giammarchi < [email protected]> wrote: > about the first example, I forgot the writable for the num property so > please read that as if I wrote: > > ```javascript > var o = {}; > Object.defineProperty(o, 'num', { > writable: true, > value: 0, > type: 'number' > }); > ``` > > the library makes possible to create a partial shim of StructType in few > lines of code, using same mechanism to guard types: > https://github.com/WebReflection/define-strict-properties/blob/master/src/StructType.js#L40 > > In this case, types are downgraded to 'number' ... and that's just an > example > > > On Sun, Mar 9, 2014 at 2:25 PM, Andrea Giammarchi < > [email protected]> wrote: > >> As written before, and explained in the project, I can write descriptors >> with optional extra properties such as: >> >> **type**, describing as string the typeof, as Function the expected >> instanceof, or as generic object as prototypeOf(expectedType) >> >> ```javascript >> >> var o = {}; >> Object.defineProperty(o, 'num', { >> value: 0, >> type: 'number' >> }); >> >> o.num = 123; // ok >> >> o.num = '123'; // throws an error, '123' is string, not number >> >> ``` >> >> The meaning of type here is the same MS choose for TypeScript but no >> breaking syntax is necessary plus types can be optionally used to described >> methods or functions too. >> >> >> ```javascript >> >> var o = {}; >> Object.defineProperty(o, 'increment', { >> value: function (much) { >> this.num += much; >> return this; >> }, >> arguments: ['number'], // 1 arg as number >> returns: Object // just an instanceof object >> }); >> >> o.num = 0; >> o.increment(1).increment(2); >> o.num; // 3 >> >> o.increment('1'); // thorws since the argument is not a typeof number >> >> ``` >> >> The received arguments can have overloads so that: >> >> ```javascript >> >> var o = {}; >> Object.defineProperty(o, 'increment', { >> value: function (much) { >> this.num += parseFloat(much); >> return this; >> }, >> arguments: [['number'],['string']], >> // 1 arg as number or 1 arg as string >> returns: Object // just an instanceof object >> }); >> >> o.num = 0; >> o.increment(1).increment(2); >> o.num; // 3 >> >> o.increment('1'); // OK >> o.num; // 4 >> >> o.increment(new Number(1)); // throws, not typeof number/string >> >> ``` >> >> Either the amount of arguments is wrong or the type won't match ... the >> signature is guarded during development time. >> >> In production, you just do not include upfront the proposed script and >> everything will work as regular ES5 preserving all behaviors and >> descriptors ... in few words, I am proposing an alternative to TypeScript >> that integrates well down to ES5. >> >> If engines would like to use types and descriptors provide such info, >> this could have ideally performance benefits too plus the code will be most >> likely less "*undefined is not defined*" prone. >> >> The library I have there, already provides all I've said behind 64 tests >> that verify the behavior is guarded and preserved with or without the >> library upfront. >> >> Compatibility with the test link [here]( >> https://github.com/WebReflection/define-strict-properties#compatibility) >> >> Best Regards >> >> >> >> >> On Sun, Mar 9, 2014 at 2:05 PM, Brendan Eich <[email protected]> wrote: >> >>> Andrea Giammarchi wrote: >>> >>>> Although my idea is more about types >>>> >>> >>> You are starting on the wrong foot there. "Types" mean something in CS. >>> Best if you start with use-cases instead of abusing the term. What code do >>> you want to write, and how exactly would it operate? >>> >>> /be >>> >> >> >
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