Josh Javascript Quiz

output of

const test = ()=> null;

console.log(typeof test())

• Object

• Function

• Undefined

• NaN

alert(({foo: () => 1}) === true) what will this code do?

• false

• True

• true

• !false

function myData(a,b,c){

argument[2] =10

alert(c)

}

myData(20,20)

• 10

• undefined

• Error

• NaN

navigator.getUserMedia(constraints, sucessCallback, errorCallback);

• Ask Access to folder

• ask permission to camera

• ask permission to audio

• ask permission to camera and audio

console.log(018-015) ==------

(a)  

consol.log(10 > 9 > 8 === true)

• True

• true

• 0

• false

parseInt(23, 10) + 242.42

• 265.41999999999996

• 265.41999999999995

• 265.42

• 265.42000000000

const isTrue = true == [];

const isFalse = true == ![];

console.log(isTrue + isFalse);

• 1

• 0

• true

• "true"

const numbers = [33, 2, 8];

numbers.sort();

console.log(numbers[1])

• 33

• 2

• 8

• 1

Answer explanation

This returns 33, but why is that?

JavaScript is a dynamically typed language, which means that all standard library functionality must, at some point, decide how to work for most, if not all, use-cases.

Always keep in mind that the following array is valid:

const array = ["1", true, 55, 1.421, "foo", {}];

Array.prototype.sort now needs to make a decision on how to handle such scenarios, and the solution is pretty straight-forward:

Convert all values to their string representation (because every value in JavaScript can always be converted to a string!), and then sort them in lexicographic order.

Which basically makes sort see the array as this:

const intermediate = ["33", "2", "8"];

And in lexicographic order, no matter how many characters a string has, comparison starts at position 0, and "3" comes before "8".

And in the end, the result is this:

["2", "33", "8"];

console.log("This is a string." instanceof String);

• true

• false

• "false"

• undefined