Integer Validation

var var1 = ["2", "a", "2017/07/11", "", undefined, null];
for(var a = 0; a < var1.length; a++) {
    var toInt = parseInt(var1[a]);
    console.log(toInt);
}
console.log("\n");

for(var a = 0; a < var1.length; a++) {
    console.log(isInteger(var1[a]));
}

function isInteger(i) {
    return i + " is valid integer? => " + ! isNaN(parseInt(i));
}