Mars exploration javascript

https://www.hackerrank.com/contests/mountblue-technologies/challenges/mars-exploration/submissions/code/1348842026

//Updated code
let ar = (s.split(/(.{3})/g).filter(o => o))
return ar.reduce((acc,val,ind)=>{
   let i = val.match(/.{1}/g)
   !(i[0] == 'S') && acc++
   !(i[1] == 'O') && acc++
   !(i[2] == 'S') && acc++
   return acc;
   //console.log(i)
},0)



function mars(s){
    let a = s.match(/S/g)
    let b = s.match(/O/g)
    let totalmsg = a.length + b.length;
    let error = s.length - totalmsg;
    
    return error;
    console.log(a,b,error);
    
}
mars("SOSSOSSOS");
# I counted the unknown characters by subtracting the known ('S' & 'O') characters from length


Other coder program
Other coders..solved by check the each character is at its own position, if not  and if unknown characters are present they counted the characters
 

function marsExploration(message) {
        let sos = "SOS";
        let count = 0;
        for (let i = 0; i < message.length; i++) {
            if (message.charAt(i) != sos.charAt(i % 3)) count++;
        }
        return count;
    } 


||


let count = 0;
    for(let i = 0; i < s.length; i+3){
        if(s.charAt(i) !== 'S'){ 
            count++;
        }
        if(s.charAt(i+1) !== 'O'){
            count++;
        }
        if(s.charAt(i+2) !== 'S'){
            count++;
        }
    }
    console.log(count);
    return count;