JavaScript Demo: Standard built-in objects

function circumference(r) {
  return parseFloat(r) * 2.0 * Math.PI;
}

console.log(circumference(4.567));
// expected output: 28.695307297889173

console.log(circumference('4.567abcdefgh'));
// expected output: 28.695307297889173

console.log(circumference('abcdefgh'));
// expected output: NaN

JavaScript Demo: Standard built-in objects - parseFloat()

​x
function circumference(r) {
  return parseFloat(r) * 2.0 * Math.PI;
}
​
console.log(circumference(4.567));
// expected output: 28.695307297889173
​
console.log(circumference('4.567abcdefgh'));
// expected output: 28.695307297889173
​
console.log(circumference('abcdefgh'));
// expected output: NaN
​