src/third_party/mozjs-45/js/src/jit-test/tests/basic/testElemInc2.js

var obj = {s: ""};
var name = "s";
for (var i = 0; i <= 13; i++)
    if (i > 8)
        obj[name]++;  // first recording changes obj.s from string to number
assertEq(obj.s, 5);