825801 - [meta] Replace use of for each...in statement in Firefox UI/app JS code with for..of

Status: RESOLVED FIXED

(Firefox :: General, defect)

Description

[Tetsuharu OHZEKI [:tetsuharu] (UTC+9)]

ECMA-357(E4X) is deprecated.
We should reduce to use of for each...in statement.

Comment 1

[Tetsuharu OHZEKI [:tetsuharu] (UTC+9)]

B2G Gaia Browser: Bug 824100
Thunderbird: Bug 824104

Comment 2

[Ben Bucksch (:BenB)]

Before removing for..each entirely, please consider:
"for..each" is very useful, makes the code a lot clearer.

for each (var item in array)
vs.
for (var item of array)
vs.
for (var i = 0; i < array.length; i++) {
  var item = array[i];
}

Unfortunately, for..of can't replace for..each. For example, when iterating over a plain object
var obj = { foo: 1, bar: 2}:
for each (var value in obj)
vs.
for (var [, value] of Iterator(obj))
for..of is nowhere near as clear to read (most important), nor convenient to type.

My plea: Before removing for..each, make sure that there is a replacement that is just as (or more) capable, clear/lean and convenient. Code readability has uttermost importance for me.

Comment 3

[Ben Bucksch (:BenB)]

Sorry, ignore last comment, I misunderstood. I thought this was about the engine.

Comment 4

[Tooru Fujisawa [:arai]]

All blocking bugs are fixed and other use are also removed in other bugs that blocks bug 1083470.