minusnon/src/string-similarity.ts

Calculates similarity between two strings

/* global exports, Map */
/**
 * Calculate similarity between two strings
 * @param {string} str1 First string to match
 * @param {string} str2 Second string to match
 * @param {number} [substringLength=2] Optional. Length of substring to be used in calculating similarity. Default 2.
 * @param {boolean} [caseSensitive=false] Optional. Whether you want to consider case in string matching. Default false;
 * @returns Number between 0 and 1, with 0 being a low match score.
 */
export const stringSimilarity = (str1: string, str2: string, substringLength: number = 2, caseSensitive: boolean = false) => {
	if (!caseSensitive) {
		str1 = str1.toLowerCase();
		str2 = str2.toLowerCase();
	}

	if (str1.length < substringLength || str2.length < substringLength)
		return 0;

	const map = new Map();
	for (let i = 0; i < str1.length - (substringLength - 1); i++) {
		const substr1 = str1.substr(i, substringLength);
		map.set(substr1, map.has(substr1) ? map.get(substr1) + 1 : 1);
	}

	let match = 0;
	for (let j = 0; j < str2.length - (substringLength - 1); j++) {
		const substr2 = str2.substr(j, substringLength);
		const count = map.has(substr2) ? map.get(substr2) : 0;
		if (count > 0) {
			map.set(substr2, count - 1);
			match++;
		}
	}

	return (match * 2) / (str1.length + str2.length - ((substringLength - 1) * 2));
};
export default stringSimilarity;