Index of anagram sub string

strings-aio-prototype.ts

interface String {
    aio(substr: string): number;
}

// S -> Space complexity
// T -> Time complexity
// n -> length of the string
// m -> length of the substr
// Overall complexity -> T(n+m) & S(n)
String.prototype.aio = function(substr: string): number {
    console.log('this:', this);
    console.log('substr:', substr);
    if (this.length === 0) {
        console.log('string is empty');
        return -1;
    }

    const substrLen = substr.length;
    if (substrLen === 0) {
        console.log('substring is empty');
        return -1;
    }

    // S(n)
    const letterPosMap = {} as Record<string, number>;
    // T(n)
    [...this].forEach((str, index) => {
        letterPosMap[str] = index;
    })
    console.debug('letterPosMap:', letterPosMap);

    if (substrLen === 1) {
        return letterPosMap[substr] || -1
    }

    let letterPositionsSum = 0;
    let letterPositionLowest = -1;
    // T(m)
    [...substr].every((substrLetter: string, index): boolean => {
        const letterFoundIndex = letterPosMap[substrLetter];
        console.debug('letterFoundIndex:', letterFoundIndex);
        if (typeof letterFoundIndex === undefined) {
            console.log('substrLetter not found:', substrLetter)
            return false; // break loop
        }
        if (index === 0 || letterFoundIndex < letterPositionLowest) {
            letterPositionLowest = letterFoundIndex;
        }
        letterPositionsSum += letterFoundIndex;
        return true;
    });
    console.debug('letterPositionLowest:', letterPositionLowest);

    return letterPositionLowest * substrLen + substrLen === letterPositionsSum
        ? letterPositionLowest
        : -1;
}

const isDebugMode = false;

if (!isDebugMode) {
    console.debug = () => {};
}

console.log('actor'.aio('cat')) // 0
console.log('actor'.aio('tar')) // -1
console.log('actor'.aio('rot')) // 2
console.log('actor'.aio('rto')) // 2