Is string good or can be made good

/*
Problem Statement: You'll be given two strings A and B, with lengths 1 <= length <= 10^6. The strings will contain only 1's and 0's. To make A a good string, you can insert B into A at any place, as many times as you want (or don't insert if you don't want). You have to print YES or NO depending on whether making A as a good string is possible.

The Definition of GOOD: A good string will never consecutively have two 1's or two 0's.
 */

interface EvaluationResult {
    has00:          boolean,
    has11:          boolean,
    isGood:         boolean,
    isBeyondSaving: boolean
}

function evaluateString(str: string): EvaluationResult {
    let has00 = false;
    let has11 = false;

    for (let i = 1; i < str.length; ++i) {
        if (str[i] === str[i - 1]) {
            // bad string
            if (str[i] === "0") {
                has00 = true;
            }
            else {
                has11 = true;
            }
        }
    }

    return {
        has00,
        has11,
        isGood:         !has00 && !has11,
        isBeyondSaving: has00 && has11
    };
}

function canStringBeMadeGood(strA: string, strB: string): "YES" | "NO" {
    // TODO: maybe handle empty string case
    const strAResult = evaluateString(strA);

    if (strAResult.isGood) {
        return "YES";
    }

    if (strAResult.isBeyondSaving) {
        return "NO";
    }

    const strBResult = evaluateString(strB);

    if (!strBResult.isGood) {
        return "NO";
    }

    if (strAResult.has00 && strB.startsWith("1") && strB.endsWith("1")) {
        return "YES";
    }

    if (strAResult.has11 && strB.startsWith("0") && strB.endsWith("0")) {
        return "YES";
    }

    return "NO";
}

console.log(canStringBeMadeGood("101", "010"));       // YES
console.log(canStringBeMadeGood("111", "010"));       // YES
console.log(canStringBeMadeGood("1110011", "01010")); // NO
console.log(canStringBeMadeGood("1001001000", "10")); // NO