String formatting

Upper and lowercase

We can change the case of strings with .toUpperCase() and .toLowerCase()

js

const quote = 'The house on Mango Street isn’t it.'

console.log(quote.toUpperCase())
console.log(quote.toLowerCase())

output

THE HOUSE ON MANGO STREET ISN’T IT.
the house on mango street isn’t it.

Slice

Slice works with strings just the same as it works with arrays.

js

const quote = 'The house on Mango Street isn’t it.'
console.log(quote.slice(13, 25))

output

Mango Street

Template literals

We can interpolate values into strings using backticks ` and ${}.

js

const author = 'Min Jin Lee'
const book = 'Pachinko'
const year = 2017

const summary = `${author} wrote ${book} in ${year}`
console.log(summary)

output

Min Jin Lee wrote Pachinko in 2017

Trim

We can remove whitespace from the beginning and end of a string with trim()

js

const quote = '   Stay awhile and listen!   '
const trimmedQuote = quote.trim()
console.log(trimmedQuote)

output

Stay awhile and listen!

Formatting numbers

We can use .toFixed() to turn a number into a string with the given number of decimals.

TIP

Note that trailing 0s are included, which makes it good for formatting currency.

js

const price = 2.39782
const displayPrice = price.toFixed(2)
console.log('£' + displayPrice)

output

£2.40