JavaScript - Math.PI property example

The Math.PI property returns π number (3.141592653589793...).

// ONLINE-RUNNER:browser;

console.log( Math.PI );

// Math.PI with circle:

// 1. Circle surface area:
var radius = 5;
var area = Math.PI * Math.pow(radius, 2);
console.log( area ); // 78.53981633974483

// 2. Circle circumference:
var radius = 5;
var circumference = 2 * Math.PI * radius;
console.log( circumference ); // 31.41592653589793

1. Documentation

2. Nilakantha series example

To calculate PI number Nilakantha series can be used.

// ONLINE-RUNNER:browser;

function computePi(iterations) {
	var approximation = 3;
  	for (var i = 0, a = 2; i < iterations; ++i) {
      	approximation += 4 / (a * (++a) * (++a));
      	approximation -= 4 / (a * (++a) * (++a));
    }
  	return approximation;
}


// Usage example:

console.log( computePi(    1 ) );  // 3.1333333333333333
console.log( computePi(    2 ) );  // 3.1396825396825396
console.log( computePi(    5 ) );  // 3.1414067184965018
console.log( computePi(   10 ) );  // 3.141565734658547
console.log( computePi(   20 ) );  // 3.141589028940776
console.log( computePi(   50 ) );  // 3.1415924109719824
console.log( computePi(  100 ) );  // 3.141592622804848
console.log( computePi(  200 ) );  // 3.1415926497127264
console.log( computePi(  500 ) );  // 3.141592653340544
console.log( computePi( 1000 ) );  // 3.141592653558594
console.log( computePi( 2000 ) );  // 3.141592653585895
console.log( computePi( 5000 ) );  // 3.141592653589538

References

1. Pi - Wikipedia