derivative in js

derivative.js

function derivative(f) {
   var h = 0.001;
   return function(x) { return (f(x + h) - f(x - h)) / (2 * h); };
}
 
console.log(" cos(2) = " + Math.cos(2));
console.log("-sin(2) = " + Math.sin(2));
console.log("(d cos/dx)(2) = " + derivative(Math.cos)(2));
 
function f(x) { return Math.pow(x, 3) + 2 * x + 1; };
var x = 12.5;
 
console.log("[6x | x = 12.5] = " + (6 * x);
console.log("(d^2 (x^3 + 2x + 1)/dx^2)(12.5) = " + 
    derivative(derivative(f))(x));

https://repl.it/IuxU

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