String Manipulation

Question 1

Concat “foo” and “bar” (all methods)

Answer 1

"foo" + "bar"
"foo".concat("bar")
'${"foo"}${"bar"}'

Question 2

Check if c in string cudacadca. Find position of c (first and last)

Answer 2

"cudacadca".includes("c")
"cudacadca".indexOf("c")
"cudacadca".lastIndexOf("c")

Question 3

Check if str starts or ends with foo

Answer 3

str.startsWith("foo")
str.endsWith("foo")

Question 4

Convert str to upper or lower case.

Answer 4

str.toUpperCase()
str.toLowerCase()

Question 5

Remove spaces from beginning, end of a str (or both)

Answer 5

str.trimStart()
str.trimEnd()
str.trim()

Question 6

Pad a string with 0 until it’s 10 chars wide (from left and right)

Answer 6

str.padStart(10, "0")
str.padEnd(10, "0")

Question 7

Extract substring"bar" from "foo bar baz" (using indexes)

Answer 7

"foo bar baz".slice(4, 7)
"foo bar baz".substring(4, 7)

Question 8

Extract last 3 chars from str

Answer 8

str.slice(-3)
str.slice(-3, str.length)

Question 9

Repalce all f with x in a str. Replace only first one.

Answer 9

str.replaceAll("f", "x")
str.replace("f", "x")

Question 10

Convert str into array of chars. "abc" => [ 'a', 'b', 'c' ]

Answer 10

str.split("")

Question 11

Join [ 'a', 'b', 'c' ] with -

Answer 11

[ 'a', 'b', 'c' ].join("-")

Question 12

Exercise
Hide all but last 4 chars of a string.

2034399002125581 => ************5581

Answer 12

const fullNumber = '2034399002125581';
const last4Digits = fullNumber.slice(-4);
const maskedNumber = last4Digits.padStart(fullNumber.length, '*');

input.slice(-4).padStart(input.length, "*")

Question 13

Check if second char of str is f (two ways).

What will happen if string length is 1 (there’s no second char).

Answer 13

str[1] == "f" // undefined if not found
str.charAt(1) // “” if not found

Question 14

Create string that is N times “X”

Answer 14

"X".repeat(n)

Question 15

How to safely compare unicode strings and why.

Answer 15

str.normalize() === str2.normalize()

• Certain characters can be represented in multiple ways in Unicode. For example:
• The letter “é” can be stored as:
  
  • Precomposed Form → “é” (U+00E9)
  • Decomposed Form → “e” + “́” (U+0065 U+0301)
• Without normalization, these two representations look the same but are actually different strings at the binary level.

Question 16

Construct string with new, print it’s value.

Answer 16

const foo = new String("foo");
console.log(foo.valueOf());
console.log(foo.toString()); // alternative

console.log(foo); // Displays: [String: 'foo'] !!!

Question 17

Create a string without parsing it’s escape characters (like \n, \ etc…)

Answer 17

String.raw`C:\Development\profile\aboutme.html`;