Line Number Adder

About Line Number Adder

This line number adder prefixes each line of text with an incrementing number, supporting customizable formatting for different use cases. Options include starting number, zero-padding width, and separator style.

Line Numbering Algorithm

JavaScript Line Numbering Implementation:

function addLineNumbers(text, options) {
  const {
    startNum = 1,
    padding = 3,
    separator = '\t'
  } = options;

  // Split on newlines (handles \r\n and \n)
  const lines = text.split(/\r?\n/);

  // Add line numbers
  return lines.map((line, index) => {
    const num = startNum + index;
    const padded = padding > 0
      ? String(num).padStart(padding, '0')
      : String(num);
    return padded + separator + line;
  }).join('\n');
}

// Usage examples:
const code = "function hello() {\n  return 'world';\n}";

// Default: 1-based, 3-digit pad, tab separator
addLineNumbers(code, {});
// 001\tfunction hello() {
// 002\t  return 'world';
// 003\t}

// Zero-based, no padding, colon separator
addLineNumbers(code, { startNum: 0, padding: 0, separator: ':' });
// 0:function hello() {
// 1:  return 'world';
// 2:}

Line Number Format Examples

Common Use Cases

• Code Review: Add line numbers to code snippets for precise referencing in pull requests and bug reports
• Legal Documents: Number lines in contracts, briefs, and court filings for citation (standard in legal publishing)
• Transcripts: Number deposition, interview, or meeting transcripts for reference
• Log Analysis: Add line numbers to log files for discussing specific entries
• Academic Writing: Number manuscript lines for peer review and editorial comments
• Poetry/Scripts: Number lines in poetry, screenplays, or scripts for analysis
• Documentation: Reference specific configuration lines in technical docs

Line Numbering Standards by Field

Line Numbering Examples

Input Text:
function greet(name) {
  console.log("Hello, " + name);
  return true;
}

Output (default: 3-digit pad, tab separator):
001	function greet(name) {
002	  console.log("Hello, " + name);
003	  return true;
004	}

Output (colon separator, no padding):
1:function greet(name) {
2:  console.log("Hello, " + name);
3:  return true;
4:}

Output (period separator, 2-digit pad):
01. function greet(name) {
02.   console.log("Hello, " + name);
03.   return true;
04. }

Removing Line Numbers

To remove previously added line numbers, use regex replacement:

Regex patterns for removing line numbers:

// Remove tab-separated numbers (001\t)
Pattern: ^\d+\t
Replace: (empty)

// Remove colon-separated numbers (1:)
Pattern: ^\d+:
Replace: (empty)

// Remove period-separated with space (1. )
Pattern: ^\d+\.
Replace: (empty)

// Remove zero-padded with any separator
Pattern: ^\d+[\t:.| ]+
Replace: (empty)

// Remove bracketed numbers ([1])
Pattern: ^\[\d+\]\s*
Replace: (empty)

Use the Find and Replace tool with regex mode enabled.

Line Numbering Best Practices

• Consistent padding: Use padding width matching expected max lines (3 digits for <1000 lines)
• Separator choice: Tab for alignment, colon for error-style, period for formal documents
• Starting at 1: Most conventions use 1-based numbering; 0-based is programming-specific
• Preserve indentation: Line numbers should prefix, not replace, existing whitespace
• Empty lines: Decide whether to number empty lines (legal: yes; code: usually yes)