CFP - Docs - truncateToNLines

truncateToNLines

(n: number) => (aString: string) => string

Truncate a string to n lines, appending an ellipses if more lines exist.

Note: both \n and \r\n are supported

Try It

const truncateTo3Lines = truncateToNLines(3)

const lf = '\n'
const crlf = '\r\n'

const notTruncated = truncateTo3Lines(` a${crlf} b${lf} c`)
console.log(notTruncated)
// is
//  a
//  b
//  c

const isTruncated = truncateTo3Lines(` a${crlf} b${lf} c${crlf} d`)
console.log('\n', isTruncated)
// is
//  a
//  b
//  c
// ...
const truncateTo3Lines = truncateToNLines(3)

const lf = '\n'
const crlf = '\r\n'

const notTruncated = truncateTo3Lines(` a${crlf} b${lf} c`)
console.log(notTruncated)
// is
//  a
//  b
//  c

const isTruncated = truncateTo3Lines(` a${crlf} b${lf} c${crlf} d`)
console.log('\n', isTruncated)
// is
//  a
//  b
//  c
// ...

Try It

const truncateTo3Lines = truncateToNLines(3)

const lf = '\n'
const crlf = '\r\n'

const notTruncated = truncateTo3Lines(
  ` a${crlf} b${lf} c`
)
console.log(notTruncated)
// is
//  a
//  b
//  c

const isTruncated = truncateTo3Lines(
  ` a${crlf} b${lf} c${crlf} d`
)
console.log('\n', isTruncated)
// is
//  a
//  b
//  c
// ...
const truncateTo3Lines = truncateToNLines(3)

const lf = '\n'
const crlf = '\r\n'

const notTruncated = truncateTo3Lines(
  ` a${crlf} b${lf} c`
)
console.log(notTruncated)
// is
//  a
//  b
//  c

const isTruncated = truncateTo3Lines(
  ` a${crlf} b${lf} c${crlf} d`
)
console.log('\n', isTruncated)
// is
//  a
//  b
//  c
// ...

Sometimes we want to limit the number of lines while indicating there's more. Below, we notice our car API is logging unnecessarily long stack traces. Let's truncate them to 5 lines.

Try It

const longStackTrace = `Error: unable to connect to database
  at connectToDb (file:///app/db/connect.mjs:25:9)
  at queryDatabase (file:///app/db/query.mjs:21:3)
  at getCarsByModel (file:///app/api/cars.mjs:15:10)
  at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
  at next (/app/node_modules/express/lib/router/route.js:131:13)
  at Route.dispatch (/app/node_modules/express/lib/router/route.js:112:3)
  at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
  at /app/node_modules/express/lib/router/index.js:277:22`

const truncateTo5Lines = truncateToNLines(5)

const trace = truncateTo5Lines(longStackTrace)
console.log(trace)
// is
// Error: unable to connect to database
//   at connectToDb (file:///app/db/connect.mjs:25:9)
//   at queryDatabase (file:///app/db/query.mjs:21:3)
//   at getCarsByModel (file:///app/api/cars.mjs:15:10)
//   at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
// ...
const longStackTrace = `Error: unable to connect to database
  at connectToDb (file:///app/db/connect.mjs:25:9)
  at queryDatabase (file:///app/db/query.mjs:21:3)
  at getCarsByModel (file:///app/api/cars.mjs:15:10)
  at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
  at next (/app/node_modules/express/lib/router/route.js:131:13)
  at Route.dispatch (/app/node_modules/express/lib/router/route.js:112:3)
  at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
  at /app/node_modules/express/lib/router/index.js:277:22`

const truncateTo5Lines = truncateToNLines(5)

const trace = truncateTo5Lines(longStackTrace)
console.log(trace)
// is
// Error: unable to connect to database
//   at connectToDb (file:///app/db/connect.mjs:25:9)
//   at queryDatabase (file:///app/db/query.mjs:21:3)
//   at getCarsByModel (file:///app/api/cars.mjs:15:10)
//   at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
// ...

Try It

const longStackTrace = `Error: unable to connect to database
  at connectToDb (file:///app/db/connect.mjs:25:9)
  at queryDatabase (file:///app/db/query.mjs:21:3)
  at getCarsByModel (file:///app/api/cars.mjs:15:10)
  at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
  at next (/app/node_modules/express/lib/router/route.js:131:13)
  at Route.dispatch (/app/node_modules/express/lib/router/route.js:112:3)
  at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
  at /app/node_modules/express/lib/router/index.js:277:22`

const truncateTo5Lines = truncateToNLines(5)

const trace = truncateTo5Lines(longStackTrace)
console.log(trace)
// is
// Error: unable to connect to database
//   at connectToDb (file:///app/db/connect.mjs:25:9)
//   at queryDatabase (file:///app/db/query.mjs:21:3)
//   at getCarsByModel (file:///app/api/cars.mjs:15:10)
//   at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
// ...
const longStackTrace = `Error: unable to connect to database
  at connectToDb (file:///app/db/connect.mjs:25:9)
  at queryDatabase (file:///app/db/query.mjs:21:3)
  at getCarsByModel (file:///app/api/cars.mjs:15:10)
  at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
  at next (/app/node_modules/express/lib/router/route.js:131:13)
  at Route.dispatch (/app/node_modules/express/lib/router/route.js:112:3)
  at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
  at /app/node_modules/express/lib/router/index.js:277:22`

const truncateTo5Lines = truncateToNLines(5)

const trace = truncateTo5Lines(longStackTrace)
console.log(trace)
// is
// Error: unable to connect to database
//   at connectToDb (file:///app/db/connect.mjs:25:9)
//   at queryDatabase (file:///app/db/query.mjs:21:3)
//   at getCarsByModel (file:///app/api/cars.mjs:15:10)
//   at Layer.handle [as handle_request] (/app/node_modules/express/lib/router/layer.js:95:5)
// ...