[рони]

Himmelin,

function fn(str)
    {
       return str.split(",").every( num => num.trim() && num == Number(num))
    }
    let str = "1,2,3,4,   5,6  ,7";
    alert(fn(str)); //true
    str = "1б2ю3,4,5,6,6";
    alert(fn(str)); //false
    str = "1,,2,4,5,,,,,6,7";
    alert(fn(str)); //false
    str = "1,2,3,4,5,yyy,6";
    alert(fn(str)); //false