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DEPRECATED. This is a rather silly package that I do not recommend using. It's easier to copy the ~20 lines of code of this package and customize that code, rather than downloading and learning how to use this package.

Add line numbers to a string.

var lineNumbers = require("line-numbers")
var string = [
  "function sum(a, b) {",
  "  return a + b;",
// 1 | function sum(a, b) { 
// 2 |   return a + b; 
// 3 | } 


  • npm install line-numbers
var lineNumbers = require("line-numbers")


lineNumbers(code, [options])

Inserts a line number at the beginning of each line in code, which is either a string or an array of strings—one for each line. All the line numbers are of the same width; shorter numbers are padded on the left side.

The return value is of the same type as code.


  • start: Number. The number to use for the first line. Defaults to 1.

  • padding: String. The character to pad numbers with. Defaults to " ".

  • before: String. String to put before the line number. Defaults to " ".

  • after: String. String to put between the line number and the line itself. Defaults to " | ".

  • transform: Function. It is called for each line and passed an object with the following properties:

    • before: options.before
    • number: Number. The current line number.
    • width: Number. The padded width of the line numbers.
    • after: options.after
    • line: String. The current line.

    You may modify the above properties to alter the line numbering for the current line. This is useful if before and after aren’t enough, if you want to colorize the line numbers, or highlight the current line.


The X11 (“MIT”) License.