Count Lines in Text — Total, Blank, and Non-Blank

Line Counting

Line counting is a fundamental text metric used across programming, writing, and data processing. A "line" is any sequence of characters terminated by a newline character.

Basic Line Count

function countLines(text) {
  if (!text) return { total: 0, blank: 0, nonBlank: 0 };
  const lines = text.split(/\r?\n/);
  const blank = lines.filter(l => l.trim() === "").length;
  return {
    total: lines.length,
    blank: blank,
    nonBlank: lines.length - blank,
  };
}

The regex /\r?\n/ handles both Unix (\n) and Windows (\r\n) line endings.

Line Ending Formats

Different operating systems use different newline conventions:

Format	Characters	Escape	Platform
LF	Line Feed	\n	Unix, macOS, Linux
CRLF	Carriage Return + Line Feed	\r\n	Windows
CR	Carriage Return	\r	Classic Mac OS (pre-X)

Modern practice is converging on LF (\n), but CRLF is still common in Windows environments and many protocols (HTTP, SMTP, CSV).

Trailing Newline Behavior

A subtle question: does a file ending with \n have an extra blank line?

"hello\nworld\n"  → 2 lines or 3?

Most text editors and wc -l count this as 2 lines — the trailing newline is a line terminator, not a separator. JavaScript's split("\n") on "hello\nworld\n" returns 3 elements (the third being empty), so you may need to adjust:

// Handle trailing newline
const lines = text.split(/\r?\n/);
if (lines[lines.length - 1] === "") lines.pop();

Lines of Code (LOC)

In software development, line counts are a common (if imperfect) metric:

• Physical LOC — total lines in the file
• Logical LOC — lines containing actual statements (excluding blank lines and comments)
• SLOC — Source Lines of Code (non-blank, non-comment lines)

Use in Data Processing

Line counting is essential for:

• CSV files — line count minus 1 gives the number of data rows
• Log files — line count represents the number of log entries
• Configuration files — tracking complexity and size
• Diff outputs — counting added/removed lines for code review metrics