CFP - Docs - replaceFirstMatch

replaceFirstMatch

(search: regex | string, replacement: string) => (aString: string) => string

Replace the first match of a string or regex.

When passing a regex, make sure the global flag is not set i.e. the regex /dog/g will cause an error.

Try It

const replaceAWithG = replaceFirstMatch('a', 'g')

replaceAWithG('aaaaah!')
// is 'gaaaah!'
const replaceAWithG = replaceFirstMatch('a', 'g')

replaceAWithG('aaaaah!')
// is 'gaaaah!'

Try It

const replaceAWithG = replaceFirstMatch('a', 'g')

replaceAWithG('aaaaah!')
// is 'gaaaah!'
const replaceAWithG = replaceFirstMatch('a', 'g')

replaceAWithG('aaaaah!')
// is 'gaaaah!'

Sometimes we want to replace the first match in text. Below, we are processing weather data from a CSV file. Our boss wants us to show the low and high columns with a symbol '<-->' to convey a range. Since low and high are the initial columns, let's replace the first comma with that symbol.

Try It

const csv = `low,high,precipitation%
72,84,0
70,85,15
62,74,40`

const conveyLowToHigh = replaceFirstMatch(',', ' <--> ')
const updateCSV = compose([
  split('\n'),
  mapValues(conveyLowToHigh),
  joinValues('\n'),
])
const updatedCSV = updateCSV(csv)
console.log(updatedCSV)
// prints
// low <--> high,precipitation%
// 72 <--> 84,0
// 70 <--> 85,15
// 62 <--> 74,40
const csv = `low,high,precipitation%
72,84,0
70,85,15
62,74,40`

const conveyLowToHigh = replaceFirstMatch(',', ' <--> ')
const updateCSV = compose([
  split('\n'),
  mapValues(conveyLowToHigh),
  joinValues('\n'),
])
const updatedCSV = updateCSV(csv)
console.log(updatedCSV)
// prints
// low <--> high,precipitation%
// 72 <--> 84,0
// 70 <--> 85,15
// 62 <--> 74,40

Try It

const csv = `low,high,precipitation%
72,84,0
70,85,15
62,74,40`

const conveyLowToHigh = replaceFirstMatch(
  ',',
  ' <--> '
)
const updateCSV = compose([
  split('\n'),
  mapValues(conveyLowToHigh),
  joinValues('\n'),
])
const updatedCSV = updateCSV(csv)
console.log(updatedCSV)
// prints
// low <--> high,precipitation%
// 72 <--> 84,0
// 70 <--> 85,15
// 62 <--> 74,40
const csv = `low,high,precipitation%
72,84,0
70,85,15
62,74,40`

const conveyLowToHigh = replaceFirstMatch(
  ',',
  ' <--> '
)
const updateCSV = compose([
  split('\n'),
  mapValues(conveyLowToHigh),
  joinValues('\n'),
])
const updatedCSV = updateCSV(csv)
console.log(updatedCSV)
// prints
// low <--> high,precipitation%
// 72 <--> 84,0
// 70 <--> 85,15
// 62 <--> 74,40