get intersection of 2 arrays of ranges

intersectRangeArrays.ts

export type Range = [number, number];

export const intersectRangeArrays = (arrA: Range[], arrB: Range[]): Range[] => {
    let result = [];

    let aLength = arrA.length;
    let bLength = arrB.length;

    let ai = 0;
    let bi = 0;

    while (ai < aLength && bi < bLength) {
        let a0 = arrA[ai][0];
        let a1 = arrA[ai][1];

        let b0 = arrB[bi][0];
        let b1 = arrB[bi][1];

        if (a1 <= b0) {
            // a ends before b
            ai++;
        } else if (b1 <= a0) {
            // b ends before a
            bi++;
        } else {
            // a overlaps b
            result.push([
                a0 > b0 ? a0 : b0,
                a1 < b1 ? a1 : b1
            ]);
            // the smaller range is considered processed
            if (a1 < b1) {
                ai++;
            } else {
                bi++;
            }
        }
    }
    return result;
};