[рони]

VSEM-DOBRA,

<script>
"use strict"
var arr = ['A','B','C','D','E'];
function combinator(matrix){
    return matrix.reduceRight(function(combination, x){
        var result = [];
        [...x].forEach(function(a){
            [...combination].forEach(function(b){
                result.push(a + b);
            });
        });
        return result;
    });
};


document.write(
    JSON.stringify(combinator(Array.from({length : 4}, () => arr )))
);
</script>