Why does javascript concatenate function names in multiple assignment to properties? -

this edge case , bad practice, made me curious js internals. can explain why chrome dev tools tells me have created function named a.a.b.b here?

note not happen unless assigning property. otherwise both , b appear refer function object named 'b':

by way, encountered here when trying answer my own question dat.gui.js .

this has nothing language spec.
it's devtools enhancement debugging convenience, ported in chrome.

remember used do?

function f() {} // notice it's named function expression f.prototype.asdf = function _asdf() { debugger; };   var f = new f(); f.asdf(); 

then in breakpoint debugging, can find method name _asdf function call stack. otherwise it's pain in ass list of (anonymous function).

in latest chrome, when assign anonymous function object property, alias attached it.

var = {}, b = {}; a.a = b.b = function() { debugger; }; a.b = b.a = function _abba() { debugger; }; 

remember, it's devtools enhancement, method remains anonymous:

a.a.name; // "" a.b.name; // "_abba" 

but it's helpful in breakpoint debugging:

a.a(); a.b(); 

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edit:

i'm not sure why alias generated a.a.b.b, looks easy kind of... stupid. however, in practice seldom a.a = b.b = func... thing (lucky). instead, define method in 1 place, , inheritence when necessary, rather copy reference directly.

so in programming practice, alias should , reflect define method. example, alias dog.bark in breakpoint maps dog.prototype.bark in source code, if it's called on puppy instance, , don't have old school named function expression.

function dog() {} dog.prototype.bark = function() { alert("woof!") }; // anonymous function expression here function puppy() {} puppy.prototype = new dog();  (new puppy()).bark(); // break point alias -> dog.bark 

one more thing, when discovered feature, can't stop thinking of - imply chrome implement es6 class soon? how exciting!