Basic

Question 1

push()

Answer 1

Adds item to the end of an array.

i.e. arr.push(“name”);

Question 2

pop()

Answer 2

Removes item from the end of an array.
i.e. arr.pop();
item can also be assigned to a variable.
i.e. myVar = arr.pop();

Question 3

shift()

Answer 3

Adds item to the front of an array.

i.e. arr.shift(“name”);

Question 4

unshift()

Answer 4

Removes item from the front of an array.
i.e. arr.unshift();
item can also be assigned to a variable.
i.e. myVar = arr.unshift();

Question 5

length

Answer 5

Can be used for the length of a string or an array.

i.e. myString.length

Question 6

===

Answer 6

Strict Equality tests both data and type. It will not convert a string to a number like == will.

Question 7

!==

Answer 7

Strict Inequality tests both data and type. It will not convert a string to a number like != will.

Question 8

How are case statements evaluated?

Answer 8

With strict equality, ===

Question 9

What are the two ways to access the properties of an object?

Answer 9

Dot Notation: myObj.property;
or
Bracket Notation: myObj["property"];
Bracket notation can also be used with a variable.
myProp="property";
myObj[myProp];

Question 10

How do you delete a property from an object?

Answer 10

delete myObj.property;

Question 11

How to you add a property to an object?

Answer 11

myObj.myProp = “property”;

Question 12

How do you check if a property exists on an object?

Answer 12

myObj.hasOwnProperty(“property”);

returns true if property exists.

Question 13

How do you generate a random number?

Answer 13

Math.random();

Returns a whole number between 0 and almost 1, but it doesn’t actually get to 1.

Question 14

How do you round down to the next whole number?

Answer 14

Math.floor();

Question 15

How do you generate a whole number between 0 and 9?

Answer 15

Math.floor(Math.random() * 10);

Question 16

How do you generate a random whole number within a range?

Answer 16

Math.floor(Math.random() * (myMax - myMin + 1)) + myMin;

Question 17

How do you initialize and object with a constructor?

Answer 17

var MotorBike = function() {
  this.wheels=2;
  this.engines=1;
  this.seats=1;
};

Question 18

describe the map function.

Answer 18

The map function iterates through an array and modifies each item by the function.

Question 19

describe the filter function

Answer 19

The filter function iterates through an array and creates a new array with items that match the filter callback.

//this filter creates a new array that includes all values not equal to 5.
array = array.filter(function(val) {
  return val !== 5;
});

Question 20

describe the sort function

Answer 20

The sort function sorts the array in place and uses a text sort if no parameters are passed. Passing in two paramaters lets you sort numbers in either direction.

//sort from largest to smallest
array.sort(function(a,b){
  return b-a;
});

//sort from smallest to largest 
array.sort(function(a,b){
  return a-b;
});

Question 21

describe reverse function

Answer 21

The reverse function reverses the order of items in an array in place.
myArray.reverse();
but can also return a reversed array
newArray = array.reverse();

Question 22

describe concat function

Answer 22

The concat function creates a new array by combining two arrays together.

newArray = oldArray.concat(otherArray);

Question 23

Describe the slice function.

Answer 23

The slice function can work on strings or arrays. It can slice a substring from a string into a new string or it can slice a section of an array into a new array. The parameters are Start and End.

var a = ['zero', 'one', 'two', 'three'];
var sliced = a.slice(1, 3);

Question 24

Describe the splice function.

Answer 24

Splice can either insert items into an array at a specific point or it can delete items from an array starting at an index and removing the specified number.

var myFish = [‘angel’, ‘clown’, ‘mandarin’, ‘sturgeon’];

myFish.splice(2, 0, 'drum'); // insert 'drum' at 2-index position
// myFish is ["angel", "clown", "drum", "mandarin", "sturgeon"]

myFish.splice(2, 1); // remove 1 item at 2-index position (that is, "drum")
// myFish is ["angel", "clown", "mandarin", "sturgeon"]

Question 25

Immutable Datatype.

Answer 25

A datatype that cannot be changed. A string is an immutable datatype, so when you concatenate a string, you are really copying the data from the original string and the appended data all into a new string.

Question 26

Mutable Datatype.

Answer 26

A datatype that can be changed. User defined objects are mutable, and setting an object = to another object results in a reference, so if there is a change, both will reflect the change.

Question 27

Describe the split function

Answer 27

The split function takes a string and splits it into an array based on a single character.
array = myString.split(‘ ‘);

Question 28

Descibe the join function

Answer 28

The join function combines all the strings in an array with a specified string between each one.

var veggies = ["Celery", "Radish", "Carrot", "Potato"];
var salad = veggies.join(" and ");