JavaScript provides several ways to extract parts of a string.

slice()

Returns a new string from the part between the begin and end positions. The original string is not mutated.

'This is my car'.slice(5) //is my car
'This is my car'.slice(5, 10) //is my

The end parameter is optional. If omitted, extraction continues to the end of the string.

Negative parameters count from the end of the string:

'This is my car'.slice(-6) //my car
'This is my car'.slice(-6, -4) //my

substring()

Similar to slice(), but with different handling of edge cases:

• If any parameter is negative, it’s converted to 0
• If any parameter is higher than the string length, it’s converted to the string length

'This is my car'.substring(5) //'is my car'
'This is my car'.substring(5, 10) //'is my'
'This is my car'.substring(5, 200) //'is my car'
'This is my car'.substring(-6) //'This is my car'
'This is my car'.substring(-6, 2) //'Th'
'This is my car'.substring(-6, 200) //'This is my car'

slice() vs substring()

The main differences:

• slice() accepts negative indexes (counting from end), substring() treats them as 0
• slice() returns empty string if start > end, substring() swaps the arguments

Use slice() when you need negative indexing. Use substring() when you want the arguments to be automatically adjusted.

split()

Splits a string into an array of substrings based on a separator:

const phrase = 'I love my dog! Dogs are great'
const tokens = phrase.split('dog')

tokens //["I love my ", "! Dogs are great"]

Split is case sensitive.

Common uses:

// Split by space to get words
'Hello World'.split(' ') //['Hello', 'World']

// Split by empty string to get characters
'Hello'.split('') //['H', 'e', 'l', 'l', 'o']

// Split by newline
'Line1\nLine2'.split('\n') //['Line1', 'Line2']

Getting String Until a Character

Use split() to get everything before a specific character:

const str = 'test-hey-ho'
str.split('-')[0] //'test'

Cutting a String into Words

const text = "Hello World! Hey, hello!"
text.split(" ")
// [ 'Hello', 'World!', 'Hey,', 'hello!' ]

Lessons in this unit:

0:	Introduction
1:	String Basics
2:	Accessing Characters
3:	Searching Strings
4:	▶︎ Extracting Substrings
5:	Transforming Strings
6:	Modifying Strings
7:	Trimming and Padding
8:	String Recipes
9:	Unicode and UTF-8
10:	Printable ASCII characters list
11:	Non-printable ASCII characters list