Math.PI

The Math.PI property represents the ratio of the circumference of a circle to its diameter, approximately 3.14159:

$$\mathtt{\mi{Math.PI}} = \pi \approx 3.14159$$

Because PI is a static property of Math, you always use it as Math.PI, rather than as a property of a Math object you created (Math is not a constructor).

The following function uses Math.PI to calculate the circumference of a circle with a passed radius.

function calculateCircumference(radius) {
  return Math.PI * (radius + radius);
}

calculateCircumference(1);  // 6.283185307179586

• Math