@technobuddha/library/levenshteinDistance/levenshteinDistance.mjs

A large library of useful functions

import create2DArray from '../create2DArray';
/**
 * Compute the levenshtein distance between two strings (similarity)
 *
 * @param input The string
 * @param comparedTo The string to compare to
 * @param __namedParameters see {@link Options}
 * @default caseInsensitive true
 * @returns the levenshteinDistance between the two strings (0 for no similarity through 1 for equal)
 */
export function levenshteinDistance(input, comparedTo, { caseInsensitive = true } = {}) {
    if (input.length === 0 || comparedTo.length === 0)
        return Math.max(input.length, comparedTo.length);
    if (caseInsensitive) {
        input = input.toLowerCase();
        comparedTo = comparedTo.toLowerCase();
    }
    const inputLen = input.length;
    const comparedToLen = comparedTo.length;
    const matrix = create2DArray(inputLen, comparedToLen, 0);
    //initialize
    for (let i = 0; i < inputLen; ++i)
        matrix[i][0] = i;
    for (let i = 0; i < comparedToLen; ++i)
        matrix[0][i] = i;
    //analyze
    for (let i = 1; i < inputLen; ++i) {
        const si = input.charAt(i - 1);
        for (let j = 1; j < comparedToLen; ++j) {
            const tj = comparedTo.charAt(j - 1);
            const cost = (si === tj) ? 0 : 1;
            const above = matrix[i - 1][j];
            const left = matrix[i][j - 1];
            const diag = matrix[i - 1][j - 1];
            let cell = Math.min(Math.min(above + 1, left + 1), diag + cost);
            //transposition
            if (i > 1 && j > 1) {
                let trans = matrix[i - 2][j - 2] + 1;
                if (input.charAt(i - 2) !== comparedTo.charAt(j - 1))
                    trans++;
                if (input.charAt(i - 1) !== comparedTo.charAt(j - 2))
                    trans++;
                if (cell > trans)
                    cell = trans;
            }
            matrix[i][j] = cell;
        }
    }
    return matrix[inputLen - 1][comparedToLen - 1];
}
export default levenshteinDistance;