function circumference(r) {
if (Number.isNaN(Number.parseFloat(r))) {
return 0;
}
return parseFloat(r) * 2.0 * Math.PI;
}
console.log(circumference('4.567abcdefgh'));
// Expected output: 28.695307297889173
console.log(circumference('abcdefgh'));
// Expected output: 0