Robor Coding Challenge Q1.

isChild.js

s1 = "abcd"
s2 = "abdc"

function isChild(str1, str2) {
    let result = []
    let count = 0
    for (let i = 0; i < str1.length; i++) {
        if (str1[i] === str2[count]) {
            result.push(str2[count])
            count++
        } else {
            while((str1[i] !== str2[count]) && (str2[count] !== undefined)) {
                count++
            }
            if (str1[i] === str2[count]) {
                result.push(str2[count])
            }
        }
    }
    return result.length
}

console.log(isChild(s1, s2))