On Apr 1, 2012, at 7:52 AM, Brendan Eich wrote: > Dmitry Soshnikov wrote: >> Oh, wait, just have read Crock's article on => functions. A Python's style >> of passing manual `this'? That's interesting (why it's not specified on the >> wiki? > > See > http://wiki.ecmascript.org/doku.php?id=strawman:arrow_function_syntax&rev=1332877190 > -- removed by next revision: > > # 2012/03/29 06:05 show differences to current version > <http://wiki.ecmascript.org/doku.php?id=strawman:arrow_function_syntax&rev=1333001151&do=diff> > strawman:arrow_function_syntax > <http://wiki.ecmascript.org/doku.php?id=strawman:arrow_function_syntax&rev=1333001151> > Updates per TC39 meeting today brendan > > > The optional leading |this| parameter without an Initialiser (parameter > default value) was long-hand for dynamic-this binding, the "thin arrow" (->) > of previous versions. We agreed with Waldemar on cutting down a list of five > "iffy" design decisions, see his meeting notes. Thin-arrow and leading |this| > fell quickly, and the desire for "one arrow" was clear. > > The detailed rationale for killing leading |this| is less clear, but without > it we have fewer function forms as you note (not sure where your 6 count came > from, but no worries). The "YAGNI" and "dynamic-this is a foot-gun" arguments > favored leaving out -> or (this, arg1, ~~~ argN) syntax. These are not > absolute judgments, obviously. They're KISS and "when in doubt, leave it out" > relative judgments. >
OK, gottcha. Thanks, Brendan. Yes, currently avoiding leading `this' seems less confusing. Dmitry P.S.: Offtopic footnote. 6 types: 1. Function Declaration (FD). Features: "hoisting", always named. 2. Function Expression (FE). Features: no "hoisting", available for immediately invoked functions (IIF). 3. Named Function Expressions (NFE). Features: no "hoisting", the same as FE actually, but because of many old (?) bugs/features, especially in IE, I put them in the separate type. Since ES5 strict they are just FE if implemented correctly. 4. Functions created via Function constructor (FF). Features: only global in the scope chain. 5. Bound functions (BF). Features: captures `this', but "dynamic" `this' in case of `new', no `prototype', no [[Scope]], no [[Construct]], but delegation to the target's, etc. 6. Arrow functions (AF). Features: captured `this', captured `this' even in case of `new'. _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
