fill123123.js

function f (min, max, length) {
    var arr = [],
        i = 0;
    
    for (; i < length; i++) {
        arr.push(
            i % (max - min + 1) + min
        );
    }
    
    return arr;
}

// usage :
//    alert( f(2, 5, 20) );

// res :
//    2,3,4,5,2,3,4,5,2,3,4,5,2,3,4,5,2,3,4,5