locutus/ruby/Array/bsearch_index.js

Locutus other languages' standard libraries to JavaScript for fun and educational purposes

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.bsearch_index = bsearch_index;
function bsearch_index(values, callback) {
    //      discuss at: https://locutus.io/ruby/Array/bsearch_index/
    // parity verified: Ruby 3.3
    //     original by: Kevin van Zonneveld (https://kvz.io)
    //          note 1: Supports Ruby's boolean "find minimum" mode and numeric "find any exact match" mode.
    //          note 2: Returns the matching index instead of the matching element.
    //       example 1: bsearch_index([1, 3, 4, 6, 8], (value) => value >= 4)
    //       returns 1: 2
    //       example 2: bsearch_index([1, 3, 4, 6, 8], (value) => (value === 4 ? 0 : 4 > value ? 1 : -1))
    //       returns 2: 2
    //       example 3: bsearch_index([1, 3, 4, 6, 8], (value) => (value === 5 ? 0 : 5 > value ? 1 : -1))
    //       returns 3: null
    if (typeof callback !== 'function') {
        throw new TypeError('bsearch_index(): callback must be a function');
    }
    if (!Array.isArray(values) || values.length === 0) {
        return null;
    }
    let low = 0;
    let high = values.length - 1;
    let candidateIndex = null;
    let mode = null;
    while (low <= high) {
        const mid = low + Math.floor((high - low) / 2);
        const value = values[mid];
        const result = callback(value, mid, values);
        if (typeof result === 'number') {
            if (mode === 'boolean') {
                throw new TypeError('bsearch_index(): callback must consistently return booleans or numbers');
            }
            mode = 'numeric';
            if (result === 0) {
                return mid;
            }
            if (result > 0) {
                low = mid + 1;
            }
            else {
                high = mid - 1;
            }
            continue;
        }
        if (mode === 'numeric') {
            throw new TypeError('bsearch_index(): callback must consistently return booleans or numbers');
        }
        mode = 'boolean';
        if (result) {
            candidateIndex = mid;
            high = mid - 1;
        }
        else {
            low = mid + 1;
        }
    }
    return candidateIndex;
}