is-subsequence.js

/**

Given two strings s and t, return true if s is a subsequence of t, or false otherwise.

A subsequence of a string is a new string that is formed from the original string by deleting some (can be none) of the characters without disturbing the relative positions of the remaining characters. (i.e., "ace" is a subsequence of "abcde" while "aec" is not).

Example 1:
Input: s = "abc", t = "ahbgdc"
Output: true

Example 2:
Input: s = "axc", t = "ahbgdc"
Output: false

 */

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isSubsequence = function(s, t) {
    let i = 0, j = 0;

    let newS = "";

    while (i < s.length && j < t.length) {
        if (s[i] === t[j]) {
            
            newS = newS + s[i];
            i++;
        } 

        j++;
    }

    return s === newS;
};



let s = "";
let t = "abc";

console.log(isSubsequence(s, t));