Strings, Arrays, and Object Methods

Question 1

Strings:

Slice()
1. What does it manipulate(is it pure)?
2. Inputs?
3. Outputs?

syntax

Answer 1

1. Does not modify the original string. pure
2. method takes 2 parameters: start position, and end position (end not included).
3. Extracts a section of a string and returns a new string. creates a new string

slice(start, end)

const str = '12 4567  910';

console.log(str.slice(0, 4));
// Expected output: "12 4"

Question 2

String

length

Its a property

exists on an instance of a string class

Answer 2

• Doe not manipulate
• property returns the length of a string

let  text = "ABCD";
let len = text.length
console.log(len)
// 4

Question 3

String

includes()

1. What does it manipulate(is it pure)?
2. Inputs?
3. Outputs?

Method

It is a case-sensitive method.

Answer 3

• Pure
• searchValue, start (defaults to 0)
  the position within the string at which to begin searching for (optional)
• Boolean value

string.includes(searchvalue, start)

**NOTE: ** it will treat the Uppercase characters and Lowercase characters differently.

Question 4

String

replace()

1. What does it manipulate(is it pure)?
2. Inputs?
3. Outputs?

Method

Answer 4

• does not mutate the original string. pure
  method replaces a specified value with another value in a string.
• pattern (string), replacement (string or a function) called for each match
• method returns a new string with one, some, or all matches of a pattern replaced by a replacement

replace(pattern, replacement)

the pattern can can also be a RegEx expression

Question 5

string

subString()

1. What does it manipulate(is it pure)?
2. Inputs?
3. Outputs?

Method

is similar to slice()

Answer 5

• does not mutate the string. pure
• extracts characters from indexStart up to but not including indexEnd.
• A new string containing the specified part of the given string.

const str = 'Gozilla';
console.log(str.substring(1, 3));
// Expected output: "oz"

substring(start, end)

begins at a specified position, and returns a specified number of characters.

Question 6

Strings

Bracket Notation

1. What does it manipulate(is it pure)?
2. Inputs?
3. Outputs?

Special Syntax

Allows to access the individual characters that make up a string.

Answer 6

• Does Nothing. property accesor, can extract string characters as read only by index
• If no character is found, [ ] returns undefined.

let text = "HELLO WORLD";
let char = text[0]; // H

syntax

Question 7

String

How to loop over a string?

Iterator Method

Answer 7

const str = "abcdefu"'
for (let i = 0; i < str.length; i++) {
console.log(str[i]);
} // "a" "b" "c" "d" "e" "f" "u"

Question 8

Strings

concat()

Answer 8

• combines two or more arguments and returns a new srting

const str = "cuoewcbeiyx"

console.log(str.concat(9));
console.log(str);

// cuoewcbeiyx9
// cuoewcbeiyx

Question 9

Strings

template literals

Template Literals

string Interpolation

Answer 9

const firstName = "Shams"
const contex = " is challenging me"

console.log(`${firstName} ${context}`);
// expects: "Shams is challenging me"

synonyms

• Template Literals
• Template Strings
• String Templates
• Back-Tics Syntax

Question 10

String

\+

Es5: “+”

Answer 10

const str1 = "wuuaao";
const str2 = ".....";
console.log(str1 + str2);

+ operaters works like concat() for strings

Question 11

Strings

toUpperCase()

Answer 11

changes case sensitive string to Upper Case

const str = "i want to love you";
console.log(str.toUpperCase());

Question 12

String

toLowerCase()

Answer 12

changes upper case charaters into case sensitive

const str = "I WANT TO GET THIS DONE Already!"

console.log(str.toLowerCase());
// expected: i want to get this done already!

Question 13

String

split()

Method

Answer 13

splits a string and returns a new array as substrings
* seperator and limit (if no parameter is placed it returns the string in the array)

const str = "I WANT TO GET THIS DONE Already!"

console.log(str.toLowerCase().split());
// [ 'i want to get this done already!' ]

const str = "I WANT TO GET THIS DONE Already!"

console.log(str.toLowerCase().split(" ", 5));
// [ 'i', 'want', 'to', 'get', 'this' ]

Question 14

Arrays

forEach()

method

Answer 14

• Iterates through arrays
• takes any value and a function to manipulate the value
• returns nothing, just iterates

const myBlessing = ["Shams", "is very lucky", "and so am I"];
//I: a function and string values
myBlessing.forEach((message) => {
    console.log(message);
}); //O: logs the Strings in the array

Shams
is very lucky
and so am I

Question 15

Arrays

map()

Answer 15

• pure
• Iterates through an array and returns a new array
• callback function, @data type value, @index, and, @array

creates a new array with the results of calling a provided function on e

Question 16

Arrays

filter()

method

Answer 16

• pure, does not change the original array
• callback function, this value
• returns a new array filled with the elements that pass a test provided by a function

array.filter(function(currentValue, index, arr), thisValue)

Question 17

Arrays

concat()

Question 18

Arrays

Array.from()

static method

Answer 18

creates a new, shallow-copied Array instance from an iterable or array-like object.

Question 19

_.defaults(object, [sources])

Answer 19

Arguments:
* object (Object): The destination object.
* [sources] (…Object): The source objects.
Returns:
* (Object): Returns object.
Impure
mutates object.