Array splice implementation to convert an existing array to target array

array_splice.js

let sourceElem = [1,2,3,4,5,6];
let targetElem = [1,2,3,4,5,6,
                  1,2,3,4,5,6,
                  2,3,4,5,6,
                  1,3,4,5,6,
                  1,4,5,6];

let resultElem = [
    1,2,3,4,5,6,
    1,2,3,4,5,6,
    '-',2,3,4,5,6,
    1,'-',3,4,5,6,
    1,'-','-',4,5,6
];
let pos = 0;
for(let i=0;i<targetElem.length;i++){
    if(pos>=sourceElem.length){
        pos = 0;
    } 
    if(targetElem[i]!=sourceElem[pos]){
        targetElem.splice(i,0,'-');
    }
    pos+=1;
}
console.log(targetElem.toString() == resultElem.toString());