"types & grammar": cover everything in this quiz

[getify]

"types & grammar": cover everything in this quiz

[getify]

Raw text dump:

JavaScript Puzzlers!
or: do you really know JavaScript?
(or: how insane do you think JavaScript actually is?)
0 / 0 of 37

    What is the result of this expression? (or multiple ones) ["1", "2", "3"].map(parseInt)
    ["1", "2", "3"] [1, 2, 3] [0, 1, 2] other

    What is the result of this expression? (or multiple ones) [typeof null, null instanceof Object]
    ["object", false] [null, false] ["object", true] other

    What is the result of this expression? (or multiple ones) [ [3,2,1].reduce(Math.pow), [].reduce(Math.pow)] ]
    an error [9, 0] [9, NaN] [9, undefined]

    What is the result of this expression? (or multiple ones) var val = 'smtg'; console.log('Value is ' + (val === 'smtg') ? 'Something' : 'Nothing');
    Value is Something Value is Nothing NaN other

    What is the result of this expression? (or multiple ones) [typeof null, null instanceof Object]
    ["object", false] [null, false] ["object", true] other

    What is the result of this expression? (or multiple ones) var name = 'World!'; (function () { if (typeof name === 'undefined') { var name = 'Jack'; console.log('Goodbye ' + name); } else { console.log('Hello ' + name); } })();
    Goodbye Jack Hello Jack Hello undefined Hello World

    What is the result of this expression? (or multiple ones) var END = Math.pow(2, 53); var START = END - 100; var count = 0; for (var i = START; i <= END; i++) { count++; } console.log(count);
    0 100 101 other

    What is the result of this expression? (or multiple ones) var ary = [0,1,2]; ary[10] = 10; ary.filter(function(x) { return x === undefined;});
    [undefined × 7] [0, 1, 2, 10] [] [undefined]

    What is the result of this expression? (or multiple ones) var two = 0.2 var one = 0.1 var eight = 0.8 var six = 0.6 [two - one == one, eight - six == two]
    [true, true] [false, false] [true, false] other

    What is the result of this expression? (or multiple ones) function showCase(value) { switch(value) { case 'A': console.log('Case A'); break; case 'B': console.log('Case B'); break; case undefined: console.log('undefined'); break; default: console.log('Do not know!'); } } showCase(new String('A'));
    Case A Case B Do not know! undefined

    What is the result of this expression? (or multiple ones) function showCase2(value) { switch(value) { case 'A': console.log('Case A'); break; case 'B': console.log('Case B'); break; case undefined: console.log('undefined'); break; default: console.log('Do not know!'); } } showCase(String('A'));
    Case A Case B Do not know! undefined

    What is the result of this expression? (or multiple ones) function isOdd(num) { return num % 2 == 1; } function isEven(num) { return num % 2 == 0; } function isSane(num) { return isEven(num) || isOdd(num); } var values = [7, 4, '13', -9, Infinity]; values.map(isSane);
    [true, true, true, true, true] [true, true, true, true, false] [true, true, true, false, false] [true, true, false, false, false]

    What is the result of this expression? (or multiple ones) parseInt(3, 8) parseInt(3, 2) parseInt(3, 0)
    3, 3, 3 3, 3, NaN 3, NaN, NaN other

    What is the result of this expression? (or multiple ones) Array.isArray( Array.prototype )
    true false error other

    What is the result of this expression? (or multiple ones) var a = [0]; if ([0]) { console.log(a == true); } else { console.log("wut"); }
    true false "wut" other

    What is the result of this expression? (or multiple ones) []==[]
    true false error other

    What is the result of this expression? (or multiple ones) '5' + 3 '5' - 3
    53, 2 8, 2 error other

    What is the result of this expression? (or multiple ones) 1 + - + + + - + 1
    2 1 error other

    What is the result of this expression? (or multiple ones) var ary = Array(3); ary[0]=2 ary.map(function(elem) { return '1'; });
    [2, 1, 1] ["1", "1", "1"] [2, "1", "1"] other

    What is the result of this expression? (or multiple ones) function sidEffecting(ary) { ary[0] = ary[2]; } function bar(a,b,c) { c = 10 sidEffecting(arguments); return a + b + c; } bar(1,1,1)
    3 12 error other

    What is the result of this expression? (or multiple ones) var a = 111111111111111110000, b = 1111; a + b;
    111111111111111111111 111111111111111110000 NaN Infinity

    What is the result of this expression? (or multiple ones) var x = [].reverse; x();
    [] undefined error window

    What is the result of this expression? (or multiple ones) Number.MIN_VALUE > 0
    false true error other

    What is the result of this expression? (or multiple ones) [1 < 2 < 3, 3 < 2 < 1]
    [true, true] [true, false] error other

    What is the result of this expression? (or multiple ones) // the most classic wtf 2 == [[[2]]]
    true false undefined other

    What is the result of this expression? (or multiple ones) 3.toString() 3..toString() 3...toString()
    "3", error, error "3", "3.0", error error, "3", error other

    What is the result of this expression? (or multiple ones) (function(){ var x = y = 1; })(); console.log(y); console.log(x);
    1, 1 error, error 1, error other

    What is the result of this expression? (or multiple ones) var a = /123/, b = /123/; a == b a === b
    true, true true, false false, false other

    What is the result of this expression? (or multiple ones) var a = [1, 2, 3], b = [1, 2, 3], c = [1, 2, 4] a == b a === b a > c a < c
    false, false, false, true false, false, false, false true, true, false, true other

    What is the result of this expression? (or multiple ones) var a = {}, b = Object.prototype; [a.prototype === b, Object.getPrototypeOf(a) === b]
    [false, true] [true, true] [false, false] other


    What is the result of this expression? (or multiple ones) function f() {} var a = f.prototype, b = Object.getPrototypeOf(f); a === b
    true false null other

    What is the result of this expression? (or multiple ones) function foo() { } var oldName = foo.name; foo.name = "bar"; [oldName, foo.name]
    error ["", ""] ["foo", "foo"] ["foo", "bar"]

    What is the result of this expression? (or multiple ones) "1 2 3".replace(/d/g, parseInt)
    "1 2 3" "0 1 2" "NaN 2 3" "1 NaN 3"

    What is the result of this expression? (or multiple ones) function f() {} var parent = Object.getPrototypeOf(f); f.name // ? parent.name // ? typeof eval(f.name) // ? typeof eval(parent.name) // ?
    "f", "Empty", "function", "function" "f", undefined, "function", error "f", "Empty", "function", error other

    What is the result of this expression? (or multiple ones) var lowerCaseOnly = /^[a-z]+$/; [lowerCaseOnly.test(null), lowerCaseOnly.test()]
    [true, false] error [true, true] [false, true]

    What is the result of this expression? (or multiple ones) [,,,].join(", ")
    ", , , " "undefined, undefined, undefined, undefined" ", , " ""

    What is the result of this expression? (or multiple ones) var a = {class: "Animal", name: 'Fido'}; a.class
    "Animal" Object an error other