Quiz: all topics

Quiz

### Quiz:

1. What is result of next line of code?

        typeof null

   Answer:
    * `null`
    * `object`
    * `undefined`

2. Which of the following function no exist for string?
    * reverse
    * replace
    * substring
    * concat

3. When executed, what value will be alerted to the screen?

        function() {
            var a = 10;
            if (a > 5) {
                a = 7;
            }
            alert(a);
        }

   Answer:
    * 7
    * 10
    * `null`
    * `undefined`

4. Assuming I call these functions in order, what value gets alerted?

        var a = 5;
        function first() {
            a = 6;
        }
        function second() {
            alert(a);
        }

   Answer:
    * 5
    * 6
    * `null`
    * `undefined`

5. There are now two variables with the same name, a. Which one does Javascript pick?

        var a = 5;
        function() {
            var a = 7;
            alert(a);
        }

   Answer:
    * 5
    * 7

6. When executed, this will pop up three alerts. In order, what are they?

        var a = 6;
        function test() {
            var a = 7;
            function again() {
                var a = 8;
                alert(a);  // First
            }
            again();
            alert(a);  // Second
        }
        test();
        ​alert(a);​  // Third

   Answer:
    * 8; 6; 7    
    * 7; 6; 8
    * 6; 7; 8
    * 8; 7; 6
    

7. What's alerted to the screen?

        function getFunc() {
            var a = 7;
            return function(b) {
                alert(a+b);
            }
        }
        var f = getFunc();
        f(5);

   Answer:
    * `null`    
    * 5
    * 7
    * 12

8. In the following example, what is foo aliased to?

        (function(foo) {
          // What is 'foo' aliased to?
        })(this);

   Answer:
    * `undefined`
    * global object (window)
    * `null`
    * `this`

9. Why do these yield different results? Write down.

        '1' + 2 +  3 ; // Equals '123'
        3  + 2 + '1'; // Equals '51'
        3  + 2 +  1 ; // Equals 6

10. How do these differ?

        function foo() {}
        // versus
        var foo = function() {};

11. Explain how to determine if a variable is an array or an object. Write few examples.
12. In one line of code, how you would make a copy of an array?

13. What’s the result of:

        function f() {
            var a = 5;
            return new Function('b', 'return a + b');
        }
        consoe.log( f()(1) );

    Answers:
    * 1
    * 6
    * undefined
    * NaN
    * error

14. What’s the result of:

        var f = function(x) {
            console.log(x)
        }

        (function() {
            f(1);
        }())

    Answers:
    * nothing
    * 1
    * error
    * depends on browser


15. What’s the result of:

        function a(x) {
            return x * 2;
        }
        var a;
        console.log(a);

    Answers:
    * error
    * 2
    * undefined
    * body of function


16. What’s the result of:

        (function() {
            return typeof arguments;
        })();

    Answers:
    * 'object'
    * 'array'
    * 'arguments'
    * 'undefined'

17. What’s the result of:

        var f = function g() { return 'test'; };
        console.log( typeof g() );

    Answers:
    * string
    * undefined
    * function
    * error

18. What’s the result of:

        console.log (f());
        var f = function () { return 1; };

    Answers:
    * null
    * undefined
    * 1
    * error

19. What’s the result of:

        function A() {}
        A.prototype.name = 'A';

        var a = new A();
        var b = new A();

        a.name = 'B';

        console.log(a.name, b.name);

    Answers:
    * 'A', 'A'
    * 'B', 'A'
    * 'B', 'B'

20. What’s the result of:

        function A() {}
        A.prototype = {
            name: 'A';
        };

        var a = new A();

        A.prototype = {
            name: 'B'
        };

        var b = new A();

        console.log(a.name, b.name);

    Answers:
    * 'A', 'A'
    * 'A', 'B'
    * 'B', 'B'

21. What’s the result of:

        function A() {
            return 5;
        }

        var a = new A();

        console.log(a);

    Answers:
    * 5
    * Object
    * undefined
    * body of function

22. What’s the result of:

        function A() {
            this.name = 'A';
        }

        var a = A();

        console.log(a.name)

    Answers:
    * 'A'
    * TypeError
    * Window
    * depends on browser

23. What’s the result of:

        function A() {}
        A.prototype = 5;

        var a = new A()

        console.log(Object.getPrototypeOf(a));

    Answers:
    * 'object'
    * 5
    * 'undefined'
    * Error

24. What are the range of heading tags available using HTML?

        * <h1> to <h3>
        * <h1> to <h6>
        * <h1> to <h8>
        * <h1> to <h7>
        * <h1> to <h9>

25. What is the difference between inline-block and block, inline-block and inline element?

26. Which color is applied to the text in block #my-id if there are next rules:

.my-class{
        color: red;
}
#my-class{
        color: white;
}
div.my-class{
        color: black;
}
div#my-class{
        color: green;
}
<div class='my-class' id="my-id">some content</div>

        * red
        * white
        * green
        * black
        
27. Coose correct order. From most importent to less.
        1. inline-style
        2. id
        3. class
        4. !important

        * 1,2,3,4
        * 2,3,4,1
        * 4,1,2,3
        * 1,3,2,4

28. What is DOM?

29. How to stop event bubbling?

30. How to stop default browser event? (ex.: prevent redirect on click by link)

31. How to create div and insert it to document with vanilla JS?

32. What are data- attributes good for?

33. Explain "hoisting"

34. Explain AJAX. Write example of AJAX call on vanilla JS.

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