javascript - Does Internet Explorer 9 choke on extra commas at the end of array and object literals? -

modern browsers , environments node.js allow {a:1, b:2,} or [1,2,3,]. has historically been problematic internet explorer. fixed in internet explorer 9?

there 2 different answers this, 1 dangling commas in object initializers , 1 dangling commas in array initializers:

for object initializers, e.g.:

var obj = {     a: 1,     b: 2,     c: 3, }; 

it's fixed in ie8 , above. test here: http://jsbin.com/uxuhopec/1 (source). ie7 , earlier throw syntax error on } after dangling comma.

for array initializers, e.g.:

var arr = [     1,     2,     3, ]; 

it "fixed" in ie9 , above. test here: http://jsbin.com/uxuhopec/2 (source). ie8 , earlier give array four entries, last 1 having value undefined. ie9 , above give 3 entries.

i put "fixed" in quotes because spec unclear whether array should have final undefined entry or not, neither behavior incorrect. it's ie went 1 way , else went other. :-)