Tests for Array.prototype.findLast On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS Array.prototype.findLast.length is 1 PASS Array.prototype.findLast.name is 'findLast' PASS [undefined, 0, null, false, ''].findLast(passUndefined) is undefined PASS [undefined, 0, null, false, ''].findLast(passZero) is 0 PASS [undefined, 0, null, false, ''].findLast(passNull) is null PASS [undefined, 0, null, false, ''].findLast(passFalse) is false PASS [undefined, 0, null, false, ''].findLast(passEmptyString) is '' PASS [0,1,2,3,4,5,6,7,8,9].findLast(passEven) is 8 PASS [0,1,2,3,4,5,6,7,8,9].findLast(passAfter5) is 9 PASS [0, null, false, ''].findLast(passUndefined) is undefined PASS [undefined, 0, false, ''].findLast(passNull) is undefined PASS [undefined, 0, null, ''].findLast(passFalse) is undefined PASS [undefined, 0, null, false].findLast(passEmptyString) is undefined PASS [1,3,5,7,9].findLast(passEven) is undefined PASS [0,1,2,3,4].findLast(passAfter5) is undefined PASS [undefined, null, false, ''].findLast(passZero) is undefined Array with holes PASS (new Array(20)).findLast(passUndefined) is undefined PASS arrayWithHoles.findLast(passUndefined) is undefined PASS arrayWithHoles.findLast(passZero) is 0 PASS arrayWithHoles.findLast(passNull) is null PASS arrayWithHoles.findLast(passFalse) is false PASS arrayWithHoles.findLast(passEmptyString) is '' PASS arrayWithHoles.findLast(passAfter5) is '' Generic Object PASS toObject([undefined, 0, null, false, '']).findLast(passUndefined) is undefined PASS toObject([undefined, 0, null, false, '']).findLast(passZero) is 0 PASS toObject([undefined, 0, null, false, '']).findLast(passNull) is null PASS toObject([undefined, 0, null, false, '']).findLast(passFalse) is false PASS toObject([undefined, 0, null, false, '']).findLast(passEmptyString) is '' PASS toObject([0, null, false, '']).findLast(passUndefined) is undefined PASS toObject([undefined, 0, false, '']).findLast(passNull) is undefined PASS toObject([undefined, 0, null, '']).findLast(passFalse) is undefined PASS toObject([undefined, 0, null, false]).findLast(passEmptyString) is undefined PASS toObject([undefined, null, false, '']).findLast(passZero) is undefined PASS toObject(new Array(20)).findLast(passUndefined) is undefined Array-like object with invalid lengths PASS var obj = { 0: 1, 1: 2, 2: 3, length: 0 }; Array.prototype.findLast.call(obj, throwError) is undefined. PASS var obj = { 0: 1, 1: 2, 2: 3, length: -0 }; Array.prototype.findLast.call(obj, throwError) is undefined. PASS var obj = { 0: 1, 1: 2, 2: 3, length: -3 }; Array.prototype.findLast.call(obj, throwError) is undefined. Modification during search PASS [0,1,2,3,4,5,6,7,8,9].findLast(findItemAddedDuringSearch) is undefined PASS [0,1,2,3,4,5,6,7,8,9].findLast(findItemRemovedDuringSearch) is undefined Exceptions PASS Array.prototype.findLast.call(undefined, function() {}) threw exception TypeError: Array.prototype.findLast requires that |this| not be null or undefined. PASS Array.prototype.findLast.call(null, function() {}) threw exception TypeError: Array.prototype.findLast requires that |this| not be null or undefined. PASS [].findLast(1) threw exception TypeError: Array.prototype.findLast callback must be a function. PASS [].findLast('hello') threw exception TypeError: Array.prototype.findLast callback must be a function. PASS [].findLast([]) threw exception TypeError: Array.prototype.findLast callback must be a function. PASS [].findLast({}) threw exception TypeError: Array.prototype.findLast callback must be a function. PASS [].findLast(null) threw exception TypeError: Array.prototype.findLast callback must be a function. PASS [].findLast(undefined) threw exception TypeError: Array.prototype.findLast callback must be a function. Callbacks in the expected order and *not* skipping holes findLast callback called with index 7 findLast callback called with index 6 findLast callback called with index 5 findLast callback called with index 4 findLast callback called with index 3 findLast callback called with index 2 findLast callback called with index 1 findLast callback called with index 0 PASS numberOfCallbacksInFindInArrayWithHoles() is 8 PASS successfullyParsed is true TEST COMPLETE