Tests for Array.prototype.filter On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS [undefined].filter(passUndefined) is [undefined] PASS (new Array(20)).filter(passUndefined) is [] PASS [0,1,2,3,4,5,6,7,8,9].filter(passEven) is [0,2,4,6,8] PASS [0,1,2,3,4,5,6,7,8,9].filter(passAfter5) is [5,6,7,8,9] PASS mixPartialAndFast.filter(passAfter5) is [5,6,7,8,9,sparseArrayLength-1] PASS toObject([undefined]).filter(passUndefined) is [undefined] PASS toObject(new Array(20)).filter(passUndefined) is [] PASS toObject([0,1,2,3,4,5,6,7,8,9]).filter(passEven) is [0,2,4,6,8] PASS toObject([0,1,2,3,4,5,6,7,8,9]).filter(passAfter5) is [5,6,7,8,9] PASS toObject(mixPartialAndFast).filter(passAfter5) is [5,6,7,8,9,sparseArrayLength-1] PASS reverseInsertionOrder([undefined]).filter(passUndefined) is [undefined] PASS reverseInsertionOrder(new Array(20)).filter(passUndefined) is [] PASS reverseInsertionOrder([0,1,2,3,4,5,6,7,8,9]).filter(passEven) is [0,2,4,6,8] PASS reverseInsertionOrder([0,1,2,3,4,5,6,7,8,9]).filter(passAfter5) is [5,6,7,8,9] PASS reverseInsertionOrder(mixPartialAndFast).filter(passAfter5) is [5,6,7,8,9,sparseArrayLength-1] ,0,[object Object] PASS reverseInsertionOrder([undefined]).filter(filterLog(passUndefined)) is [undefined] PASS reverseInsertionOrder(new Array(20)).filter(filterLog(passUndefined)) is [] 0,0,[object Object] 1,1,[object Object] 2,2,[object Object] 3,3,[object Object] 4,4,[object Object] PASS reverseInsertionOrder([0,1,2,3,4]).filter(filterLog(passEven)) is [0,2,4] 0,0,[object Object] 1,1,[object Object] 2,2,[object Object] 3,3,[object Object] 4,4,[object Object] 5,5,[object Object] 6,6,[object Object] 7,7,[object Object] 8,8,[object Object] 9,9,[object Object] 10099,10099,[object Object] PASS reverseInsertionOrder(mixPartialAndFast).filter(filterLog(passAfter5)) is [5,6,7,8,9,sparseArrayLength-1] ,0, PASS ([undefined]).filter(filterLog(passUndefined)) is [undefined] PASS (new Array(20)).filter(filterLog(passUndefined)) is [] 0,0,0,1,2,3,4 1,1,0,1,2,3,4 2,2,0,1,2,3,4 3,3,0,1,2,3,4 4,4,0,1,2,3,4 PASS ([0,1,2,3,4]).filter(filterLog(passEven)) is [0,2,4] 0,0,0,1,2,3,4,5,6,7,8,9, 1,1,0,1,2,3,4,5,6,7,8,9, 2,2,0,1,2,3,4,5,6,7,8,9, 3,3,0,1,2,3,4,5,6,7,8,9, 4,4,0,1,2,3,4,5,6,7,8,9, 5,5,0,1,2,3,4,5,6,7,8,9, 6,6,0,1,2,3,4,5,6,7,8,9, 7,7,0,1,2,3,4,5,6,7,8,9, 8,8,0,1,2,3,4,5,6,7,8,9, 9,9,0,1,2,3,4,5,6,7,8,9, 10099,10099,0,1,2,3,4,5,6,7,8,9, PASS (mixPartialAndFast).filter(filterLog(passAfter5)) is [5,6,7,8,9,sparseArrayLength-1] PASS [1,2,3].filter(function(i,j,k,l,m){ return m=!m; }) is [1,2,3] PASS successfullyParsed is true TEST COMPLETE