https://leetcode.com/problems/one-edit-distance/

oneEditDistance.js

var isOneEditDistance = function(s, t) {
    if(Math.abs(s.length - t.length) > 1) return false;
    if(s === t) return false;
    
    let longer; let shorter;
    if(s.length > t.length){
        [longer, shorter] = [s, t];
    }else{
        [longer, shorter] = [t, s];
    }
    
    for(let i=0; i<longer.length; i++){
        if(longer[i] !== shorter[i]){
            return (
                longer.slice(i+1) === shorter.slice(i) || // insert into shorter
                // delete from longer. Same as add to shorter so don't bother
                longer.slice(i+1) === shorter.slice(i+1)  // edit to match
            )
        }
    }
    
    return true;
};