Functions

Question 1

What is a function?

Answer 1

a function is a procedure that lets you extract code and run it as a separate unit

Question 2

what is a function name without parentheses?

Answer 2

Without parentheses a function like funcName() is not a function call but simply the name of the function. The value being a function object representing the function in question

Question 3

what scope do parameters have?

Answer 3

Parameters arelocal variablesonly available within the function’s body

Question 4

What happens when you nest a function in another function?

Answer 4

These are private functions which can only be called within the parent functions definition.

Question 5

What scope do function names have?

Answer 5

Function names are either global or local, depending on whether the function is at the program’s top level or nested inside a class, object, or another function.

Question 6

What are arguments?

Answer 6

Arguments are objects or primitive values passed to a function

Question 7

What are parameters?

Answer 7

parameters are declarations for the local variables used inside the function to access the arguments.

Question 8

What happens if you provide too few/too many arguments?

Answer 8

If you provide too few arguments, the parameters and variables that correspond to the missing arguments will receive a value ofundefined. Additional arguments will be ignored if you provide too many

Question 9

What is a function which only returns a boolean called?

Answer 9

A predicate

Question 10

What is the implicit return value of most JS functions?

Answer 10

Undefined

Question 11

What is an explicit return value?

Answer 11

An explicit return value is when you provide an specific overriding return in the function definition

Question 12

how do you define default parameters?

Answer 12

function say(text = “hello”) {
console.log(text + “!”);
}

Question 13

How is a method different than a function? How can we tell the difference?

Answer 13

Methods are functions built into existing objects. We can tell because they use a period for invocation. ‘xyzzy’.toUpperCase()

Question 14

What’s the difference between reassignment and mutation?

Answer 14

To change a variable can either change what value is assigned (orbound) to a variable or we can change the value of the thing that is bound to the variable. The former is known asreassignmentwhile the latter is known asmutation.

Question 15

Can we change primitives?

Answer 15

No. Primitive values are immutable.

Question 16

What is function composition?

Answer 16

Function composition is when we use a function call as an argument to another function. Because all function calls evaluate to a value, this is the same as passing the return value of the second function to the first.

Question 17

What are the three ways of defining a function?

Answer 17

Function declaration,
Function expressions, and arrow functions

Question 18

which methods of function definition allow you to call a function before it is defined.

Answer 18

Only function declaration

Question 19

What is function declaration?

Answer 19

function functionName(zeroOrMoreArguments…) {
// function body
}

Question 20

What is a function expression?

Answer 20

let greetPeople = function () {
console.log(“Good Morning!”);
};

Any function definition that doesn’t have the word function at the very beginning is a function expression.

Question 21

What does it mean that JS functions are ‘first-class-functions’?

Answer 21

This means that JS treats functions like any other variable. Which in fact they are, all JavaScript functions are objects

Question 22

how do you define an arrow function?

Answer 22

let add = (a, b) => a + b;

Question 23

Can we omit return statements in arrow functions?

Answer 23

We can omit return statements in arrow functionswhen and only when the function body contains a single expression that is not itself surrounded by curly braces

Question 24

Can parameter parentheses can only be omitted in arrow functions?

Answer 24

parameter parentheses can only be omitted if the function has a single simple parameter

Question 25

What is the call stack?

Answer 25

the call stack is a mechanism for an interpreter (like the JavaScript interpreter in a web browser) to keep track of its place in a script that calls multiple functions — what function is currently being run and what functions are called from within that function, etc.

Question 26

What order does JS add/remove frames from the call stack

Answer 26

the call stack puts information about the current function on the top of the stack, then removes that information when the function returns.

Question 27

What are the units on the call stack called?

Answer 27

Stack Frames

Question 28

What is the initial stack frame referred to as?

Answer 28

The main function

Question 29

What is a limitation of recursive functions?

Answer 29

recursive functions can break the call stack by exceeding the call stack length if they keep calling themselves too many times.