var arraystring = ['test', 'cat', 'meow'];
checkEarraystring(arraystring,letter = "e");

function checkEarraystring (arraystring,letter = "e"){
    var arr = [];
    for (var i=0; i<arraystring.length;i++) {
            arr[i] = arraystring[i]>= letter;
    }
    return arr;
}
alert(checkEarraystring(arraystring))