MutationObserver tests - Firefox 19 - Reddit Enhancement Suite v4.1.5

0 README.md

1. Declare var MutationObserver in the global scope (i.e. outside of a function) in the plugin

2. Observe that window.MutationObserver is undefined.
   (In RES v4.1.5, this manifests as MutationObserver == undefined || null == null)

3. Remove var MutationObserver from the global scope code.

4. Observe that window.MutationObserver is a constructor function, is truthy, and logs as null unless you cast it a little.
   (After fixing this in RES, this manifests as MutationObserver == the constructor)

5. Leave out the var MutationObserver and add a variable that points to the MU constructor.

6. Observe that the pointer works sanely.
   In other words, Firefox will let you store the constructor and use it later.

---

Conclusion: RES should avoid var MutationObserver and instead use BrowserDetect.MutationObserver = window.MutationObserver || ... null and, to create an instance, var mutationObserver = new BrowserDetect.MutationObserver(function(m) { ... });

(This is not the only option, but it seems the tidiest).

1 with var MutationObserver .js

var MutationObserver;

window.console.log(0, window.MutationObserver);
window.console.log(1, typeof window.MutationObserver);
window.console.log(2, (window.MutationObserver));
window.console.log(3, typeof (window.MutationObserver));
window.console.log(4, window.MutationObserver + "");
window.console.log(5, "" + window.MutationObserver);
window.console.log(6, window.MutationObserver || false);
window.console.log(7, typeof(window.MutationObserver || false));
window.console.log(8, false || window.MutationObserver);
window.console.log(9, typeof(false || window.MutationObserver));
window.console.log(10, window.MutationObserver || 1);
window.console.log(11, typeof(window.MutationObserver || 1));
window.console.log(12, 1 || window.MutationObserver);
window.console.log(13, typeof(1 || window.MutationObserver));
window.console.log(14, window.MutationObserver + 1);
window.console.log(15, 1 + window.MutationObserver);

2. MutationObserver is undefined

info: reddit_res: 0 null
info: reddit_res: 1 undefined
info: reddit_res: 2 null
info: reddit_res: 3 undefined
info: reddit_res: 4 undefined
info: reddit_res: 5 undefined
info: reddit_res: 6 false
info: reddit_res: 7 boolean
info: reddit_res: 8 null
info: reddit_res: 9 undefined
info: reddit_res: 10 1
info: reddit_res: 11 number
info: reddit_res: 12 1
info: reddit_res: 13 number
info: reddit_res: 14 null
info: reddit_res: 15 null

3. no var MutationObserver.js

// var MutationObserver;

window.console.log(0, window.MutationObserver);
window.console.log(1, typeof window.MutationObserver);
window.console.log(2, (window.MutationObserver));
window.console.log(3, typeof (window.MutationObserver));
window.console.log(4, window.MutationObserver + "");
window.console.log(5, "" + window.MutationObserver);
window.console.log(6, window.MutationObserver || false);
window.console.log(7, typeof(window.MutationObserver || false));
window.console.log(8, false || window.MutationObserver);
window.console.log(9, typeof(false || window.MutationObserver));
window.console.log(10, window.MutationObserver || 1);
window.console.log(11, typeof(window.MutationObserver || 1));
window.console.log(12, 1 || window.MutationObserver);
window.console.log(13, typeof(1 || window.MutationObserver));
window.console.log(14, window.MutationObserver + 1);
window.console.log(15, 1 + window.MutationObserver);

4. no var MutationObserver results

info: reddit_res: 0 null
info: reddit_res: 1 function
info: reddit_res: 2 null
info: reddit_res: 3 function
info: reddit_res: 4 [object MutationObserver]
info: reddit_res: 5 [object MutationObserver]
info: reddit_res: 6 null
info: reddit_res: 7 function
info: reddit_res: 8 null
info: reddit_res: 9 function
info: reddit_res: 10 null
info: reddit_res: 11 function
info: reddit_res: 12 1
info: reddit_res: 13 number
info: reddit_res: 14 [object MutationObserver]1
info: reddit_res: 15 1[object MutationObserver]

5. no var, variable pointer to MutationObserver.js

// var MutationObserver;

var mo = window.MutationObserver;
window.console.log(0, mo);
window.console.log(1, typeof mo);
window.console.log(2, (mo));
window.console.log(3, typeof (mo));
window.console.log(4, mo + "");
window.console.log(5, "" + mo);
window.console.log(6, mo || false);
window.console.log(7, typeof(mo || false));
window.console.log(8, false || mo);
window.console.log(9, typeof(false || mo));
window.console.log(10, mo || 1);
window.console.log(11, typeof(mo || 1));
window.console.log(12, 1 || mo);
window.console.log(13, typeof(1 || mo));
window.console.log(14, mo + 1);
window.console.log(15, 1 + mo);

6. You can get a pointer to MutationObserver which acts normally

info: reddit_res: 0 null
info: reddit_res: 1 function
info: reddit_res: 2 null
info: reddit_res: 3 function
info: reddit_res: 4 [object MutationObserver]
info: reddit_res: 5 [object MutationObserver]
info: reddit_res: 6 null
info: reddit_res: 7 function
info: reddit_res: 8 null
info: reddit_res: 9 function
info: reddit_res: 10 null
info: reddit_res: 11 function
info: reddit_res: 12 1
info: reddit_res: 13 number
info: reddit_res: 14 [object MutationObserver]1
info: reddit_res: 15 1[object MutationObserver]