Boost if exact match

[AJamesPhillips]

Thank you very much for the code based on the Sørensen–Dice coefficient.

I made a minor addition to increase the score when there's an exact match at the start, or part way through. This is 10 minutes work so lacks any of the consideration you've put into the existing code. I'm also sure there must be many additional well considered and published improvements. I'm sharing this variant in case someone else finds it adds value to their application.

Thank you again! AJP

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

	let boost = 1
	if (str1.startsWith(str2) || str2.startsWith(str1)) boost = 4
	else if (str1.includes(str2) || str2.includes(str1)) boost = 2

	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++
		}
	}

	const score = (match * 2) / (str1.length + str2.length - ((substringLength - 1) * 2))

	return Math.min(1, score * boost)
}