@ncbijs/fasta

Parse FASTA format sequences into typed records. Zero dependencies.

Installation

npm install @ncbijs/fasta

Usage

import { parseFasta } from '@ncbijs/fasta';

const text = `
>NP_000537.3 cellular tumor antigen p53 isoform a [Homo sapiens]
MEEPQSDPSVEPPLSQETFSDLWKLLPENNVLSPLPSQAMDDLMLSPDDIEQWFTEDPGP
DEAPRMPEAAPPVAPAPAAPTPAAPAPAPSWPLSSSVPSQKTYPQGLNGTVNLPGRNSFEV
`;

const records = parseFasta(text);

console.log(records[0].id); // 'NP_000537.3'
console.log(records[0].description); // 'cellular tumor antigen p53 isoform a [Homo sapiens]'
console.log(records[0].sequence); // 'MEEPQSDPSVEPPLSQETFSDLWKLL...'

API

parseFasta(text: string): Array<FastaRecord>

Parses a FASTA-formatted string into an array of records.

• Header lines (>) split into id (first word) and description (rest)
• Multi-line sequences are concatenated
• Comment lines (;) and blank lines are skipped
• Handles GenBank, UniProt/SwissProt, and NCBI identifier formats

Error handling

parseFasta is a pure synchronous parser. It does not throw on malformed input — records without a header line (>) are silently skipped, and empty sequences produce records with an empty sequence string.

FastaRecord

interface FastaRecord {
  readonly id: string;
  readonly description: string;
  readonly sequence: string;
}