Need to replace non-standard for-each with one of: * for-of * for-in * array.map/array.filter for array-comprehension as a part of bug 1083470. converting rules are following: * for-each * for each (let x in array) { ... } -> for (let x of array) { ... } * for each (let x in object) { ... } -> for (let key in object) { let x = object[key]; ... } * for each (let [key, value] in Iterator(object)) { ... } -> for (let key in object) { let value = object[key]; ... } * for each (let x in array) { ... } where array can be null or undefined -> if (array) { for (let x of array) { ... } } * legacy array comprehension with for-each (newer array comprehension is now also a non-standard feature, I'd like to go with map/filter) * [EXPR for each (x in array)] -> array.map(x => EXPR) * [EXPR for each (x in array) if (COND)] -> array.filter(x => COND).map(x => EXPR) * [x for each (x in array) if (COND)] -> array.filter(x => COND) * [EXPR for each ([i, x] in Iterator(array)) if (g(x, i)] -> array.filter((x, i) => g(x, i)).map((x => EXPR) * [EXPR for each (x in arraylike)] -> Array.from(arraylike).map(x => EXPR) * [EXPR for each (x in string)] -> Array.prototype.slice.call(string).map(x => EXPR) // Array.from behaves differently for surrogate-pair

Almost green on try run: https://treeherder.mozilla.org/#/jobs?repo=try&revision=77c5563839da

here's the result of investigation for some complicated case.

Comment on attachment 8677295 [details] [diff] [review] Remove for-each from docshell/. Crazy inconsistency in the language if 'in' can deal with null/undefined but 'of' can't, IMHO.

https://hg.mozilla.org/integration/mozilla-inbound/rev/05bb7ca32591b299a15588ac01440ad9a91f67f8 Bug 1217315 - Remove for-each from docshell/. r=smaug