JS String Methods - Part 7

endsWith() and startsWith(). Strings only, sorry not sorry RegEx.

In this post, skip to:

• endsWith()
• startsWith()
• Practice!

endsWith

endsWith() will check if a string ends with the characters of the string you feed it, returning true or false.

It takes two parameters: the first one consists of the characters you want to find at the end of the string - and this can't be a regular expression.

The second parameter is optional, and it's the end position where you expect your first parameter to end. If you don't provide one it'll just default to the .length of the string, to try and find the first parameter at the end.

To help visualize it better:

let string = "I don't see any train. All I see is a giant sneaker."

string.length
//output: 52

string.endsWith('sneaker')
//output: false

string.endsWith('.')
//output: true

string.endsWith(' sneaker.')
//output: true

string.endsWith('sneaker', string.length - 1)
//output: true

string.endsWith('sneaker', 51)
//output: true

string.endsWith('train', '21')
//output: true

startsWith

startsWith() goes the other way around! It'll check if a string starts with a string parameter you feed it, start checking from 0 by default, and return true or false.

The second, optional parameter is a number representing the position in the string where you expect the first parameter to start!

let string = "I don't see any train. All I see is a giant sneaker."

string.startsWith("I don't")
//output: true

string.startsWith("don't", 2)
//output: true

string.startsWith("don't", "2")
//output: true

string.startsWith('.')
//output: false

string.startsWith('.', 21)
//output: true

Some practice exercises

These 8-kyu Kata are quick and fun:

• Remove an exclamation mark from the end of string
• Are You Playing Banjo?

As usual, JsKatas has awesome practice for startsWith and endsWith