Subsequence problem. I solved this problem while in a meeting, trying to understand how difficult it would be.

subsequence.js

function isSubsequence(s: string, t: string): boolean {
    let aIdx = 0;
    let bIdx = 0;
    while ((aIdx < s.length) && (bIdx < t.length)) {
            const aChar = s.charAt(aIdx);
            const bChar = t.charAt(bIdx);
            if (aChar === bChar) {
                aIdx++;
            }
		bIdx++;
	}
    return aIdx === s.length;
};