Wrong number of iterations for objects that contain numeric keys

[francois2metz]

This is an ios only bug that also happened on lodash.

lodash/lodash#799

Here is the original testcase updated for underscore: http://jsfiddle.net/rcsz27v1/2/

The result should be 3, but on ios it's 51.

It happens on underscore 1.8.2 as well as 1.7.0.

[megawac]

@francois2metz IOS8? Want to make a PR with a failing test case (otherwise I can do it later)?

[francois2metz]

@megawac Yep, IOS8. I'll create the pull request.

[jridgewell]

It's coming up because isArrayLike() is being improperly JIT'd.

var getLength = function(array) {
  return array.length;
};

// JIT getLength with only arrays
for (var i = 0; i < 1000; i++) getLength([]);

getLength({5: 'test'}); // => 6

[osolo]

There is further discussion of this topic at http://stackoverflow.com/questions/28155841/misterious-failure-of-jquery-each-and-underscore-each-on-ios.

The problem is that the iOS bug causes a length property to incorrectly appear for these objects, which causes each to try to iterate the object as an array.

The solution is to check for obj.hasOwnProperty('length'), which I can confirm is immune to this bug.

Also see this summary in the related bug I filed against jQuery: jquery/jquery#2145

[drawveloper]

Got bitten by this bug today. One entire afternoon debugging an iPhone 6... It seems @osolo solution works. Do you guys need a PR?

[jridgewell]

@firstdoit: #2094

[drawveloper]

@jridgewell nice! sorry I missed that.