@woosh/meep-engine/src/core/collection/array/binarySearchLowIndex.js

Pure JavaScript game engine. Fully featured and production ready.

/**
 * @template T,V
 * @param {T[]} array
 * @param {V} el
 * @param {function(V,T):number} compareFunction
 * @param {number} [minIndex]
 * @param {number} [maxIndex]
 * @return {number} Index
 */
export function binarySearchLowIndex(array, el, compareFunction, minIndex = 0, maxIndex = array.length - 1) {

    let result = 0;

    while (minIndex <= maxIndex) {

        const pivotIndex = (minIndex + maxIndex) >> 1;

        const cmp = compareFunction(el, array[pivotIndex]);

        if (cmp > 0) {
            minIndex = pivotIndex + 1;
        } else if (cmp < 0) {
            maxIndex = pivotIndex - 1;
            result = maxIndex;
        } else {
            //set low boundary for next step based on assumption that upper bound is higher than lower bound
            result = pivotIndex;
            break;
        }

    }

    return result;
}