JS Basics (HR)

Question 1

what is the type of “hi”

Answer 1

string literal

Question 2

what type is - true - and what cn it represent?

Answer 2

boolean. represents opposing ideas, such as on vs off, positive vs negative, present vs absent, or truth vs falsehood

Question 3

what is the type - underfined - and what does it represent?

Answer 3

undefined value represents an unknown or undetermined state. Will receive this value, when someone or some system is trying to indicate to you that the info you’re inquired about could not be found.

Question 4

what is the type of 3

Answer 4

number literal

Question 5

what do you need in order to make calculations

Answer 5

Operators. Operators are things like plus, known as the addition operator, and they imply that some work should be done on the values around them. Research operator precedence if i want to learn more about order of operations

Question 6

What are expressions?

Answer 6

A set of literals, variables and operators intended to tell your computer how to take one small step forward in a larger computation. When processes at run time, every expression will have a result value. It will “evaluate to”

Question 7

where to go for understanding how my JS interpreter will process my code, and it what order.

Answer 7

http://jsparse.meteor.com

Question 8

what is this type of statement? log((3+1)* 2);

Answer 8

expression statement. the semicolon has effect of discarding the result value of the full, compound expression occupying the entire line, allowing the interpret to proceed with clean slate

Question 9

how would you describe this? var result = (3+1) * 2;

Answer 9

Variable declaration statement.

Question 10

describe a variable

Answer 10

storing a previously-computed value by naming it with a variable. A variable can be thought of as a “label” or “alias” that points to some value stored

Question 11

What will the var other log to the console in this scenario?
var result = (3+1)*2;
log(result);
var other = result;
result = 5;
console.log(other);

Answer 11

8. This is because other will store the original value, since our new (overwriting) assignment operation told teh interpreter to make result point to something different, but it did not tell the interpreter to make other point to something different.

Question 12

what is it called to define an object like this: var myObj = {};

Answer 12

Object literal

Question 13

In an object, what is the combination of one key and one value called?

Answer 13

property

Question 14

What does a failed property lookup evaluate to?

Answer 14

undefined

Question 15

when accessing accessing or assigning properties with bracket access

Answer 15

the value, if not already a string, gets stringified before lookup

Question 16

True/False -> you can do a for/in loop on arrays

Answer 16

True

Question 17

True/False -> arrays can have non-integer keys

Answer 17

True, but they do not count towards their “length”

Question 18

What are “enumerable” properties of an array

Answer 18

they are certain built-in properties that Javascript knows you don’t want to iterate over in a for (with semicolons) loop for example

Question 19

are functions, objects?

Answer 19

yes, they can store properties just like any other object. you can’t run function.length on them though, as that is reserved for Arrays. you could iterate through them only with for/in loops though

Question 20

what is it called to activate whatever behavior that function is capable of?

Answer 20

to Invoke.

Question 21

how to you make a function run?

Answer 21

you put brackets () at the end of it. this will make what is inside the {}, known as the body, run.

Question 22

what is the work done to the environment around it (such as logging a message to the console) called?

Answer 22

a Side Effect

Question 23

what always returns if there is no “return” statement in a function?

Answer 23

undefined

Question 24

will the lines inside the {} run automatically?

Answer 24

No, only when the function is invoked with (), will it run. It will never run, not even once, until it is invoked with a ()

Question 25

what is “hi” considered to be when calling the function fun(“hi”);

Answer 25

the Argument

Question 26

talk about the arguments object in a function

Answer 26

it is a special keyword called ‘arguments.’ instead of being assigned to a value with the assignment operator, the arguments keyword just automatically holds a brand new array every time you invoke the contain function. the elements coin the array will be the arguments that got passed during the current invocation

Question 27

how to create an parameter via the arguments object?

Answer 27

NOT LIKE THIS:
var fun = function(input){
console.log(input.toUpperCase());
}

BUT LIKE THIS:
var fun = function(){
	var input = arguments[0];
	console.log(input.toUpperCase());
}

Question 28

what happens when you refer to a parameter by its name, even though no corresponding argument was passed in during the invocation?
var fun = function(input){
	console.log(input.toUpperCase());
}

fun();
//logs what??

Answer 28

undefined

Question 29

what will happen if you try to refer to arguments from within a nested function?

Answer 29

that reference to arguments will refer to an array of values that were passed in to the inner function

Question 30

can you use the same variable for parameters in nested functions?

Answer 30

Yes, you can use the same variable names

Question 31

setTimeout, is a native function that takes two parameters - (myFunk, time to run myFunk). how would you run myFunk, which takes a parameter? (Note: setTimeout does not allow for adding a parameter to myFunk

Answer 31

Wrap myFunk in an anonymous function, that passes in a parameter into myFunk like this:

setTimeout(function(){
myFunk(‘hi’);
}, 1000);

Question 32

Are you allowed to assign properties to an Object that is set to “null” or “undefined”?

Answer 32

Nope. it will throw an error

Question 33

what are immutable values?

Answer 33

It means you can’t modify them (by adding properties to them). Immutable objects include: booleans, Strings, and Numbers

Question 34

what is a method?

Answer 34

an object’s property that is pointing to a function