[javascript]Calculating PI

pi.js

// calculating PI
console.log(Math.PI);

var pi1 = function (n) {
    // Bailey-Borwein-Plouffe
    var r = 0;
    for (var i = 0; i < n; i++) {
        var b = 8 * i;
        r += (4/(b+1) - 2/(b+4) - 1/(b+5) - 1/(b+6)) / Math.pow(16, i);
    }
    return r;
};
console.log(pi1(11)); // === Math.PI


var pi2 = function (n) {
    // Adamchik-Wagon
    var r = 0;
    for (var i = 0; i < n; i++) {
        var b = 4 * i;
        r += (2/(b+1) + 2/(b+2) + 1/(b+3)) / Math.pow(-4, i);
    }
    return r;
};
console.log(pi2(24)); // pi2(24) === pi2(25)


var pi0 = function (n) {
    // Leibniz
    var r = 0;
    for (var i = 0; i < n; i++) {
        r += (i % 2 === 0 ? 1 : -1) / (2 * i + 1);
    }
    return 4 * r;
};
console.log(pi0(10000000)); // until 7-digits
//console.log(pi0(1000000000)); // until 9-digits

result

$ node pi.js 
3.141592653589793
3.141592653589793
3.1415926535897927
3.1415925535897915