1 questions to solve.

Instructions
1. This quiz goes to full-screen once you press the Start button, or any Next button after exiting the quiz window.
2. At the end of the quiz, you are able to review all the questions that you answered wrong and see their explanations.
Arrays can be created using the:
Both methods create an array in JavaScript. For more info please check out Creating arrays in JavaScript.
How to access the second element of the array `arr = [3, 7, 10]`?
Array indexes start at `0` - the first element is at index `0`, the second is at index `1` and so on and so forth. To access the second element, we'll use bracket notation along with the index `1`. This goes with choice D).

Arrays can have arrays as elements.
True or false?
In JavaScript, arrays can definitely contain arrays and if this is the case, we have the concept of array dimensions into the game. More info on Array Dimensions.
Define a 2D array.
What would `arr.indexOf(0)` and `arr.indexOf(1)` return respectively, if `arr` holds the array `[1, 5, 8]`?
`indexOf()` gives the index of a given value (if found) in the array.
Which property on arrays can be used to loop through them?
`length` gives the total number of elements in an array which can then be used to loop through it.
How to replace the second element in the array `arr = [1, 7, 9]` with the value `8`?
Array indexes start at 0. Hence the second element would be at index 1. For more info on the basics of the basics of arrays head over to Creating Arrays.
The expressions `arr` and `arr.shift()` do the same thing on a given array. Yes or no?
`arr` returns the element at position 0 and `arr.shift()` removes the first element from the array and returns it.
What does `new Array(10)` return?
`i` is 5 hence `i < 5` is false and thus the loop won't procede any further.
What is the value of `passed` in the following code?
``````var marks = [30, 35, 42, 20, 15];
var passed = marks.every(function(m) {
return m > 40;
});``````
`every` returns `true` or `false` based on whether every element in the array meets a given condition or not.
Can we check for an array using the `typeof` operator? If not then why?
To check for arrays in JavaScript we can't rely on `typeof` because it returns `"object"` for both array and pure objects! See Arrays Basic Concepts for more details.
What will the following code log?
``````var arr = [1, 66, 20];
arr.length = 0;

console.log(arr);``````
Setting the `length` property of an array to a given value reduces (or expands) the array to that very length. In this case, the expression `arr.length = 0` makes `arr` equal to `[]`, on which `arr` logs `undefined`. This goes with choice (C).
What will the following code log?
``````var arr = [10, 50, 88];
arr.filter(function(e) {
return e > 10;
});

console.log(arr);``````
Line 2 here returns the array `[50, 88]`, which simply has no consequence. `arr` is nonetheless still the same, as `filter()` doesn't work on the original array. Likewise line 6 returns `[10, 50, 88]` - the same old value of `arr` - which goes with choice A).