[JavaScript] Simple implementation of Newton-Raphson method

Author: kneth

JavaScript/newton.js

@@ -0,0 +1,35 @@
+// Simple Newton-Raphson solution of the equation v(t) = 100/3.6 where v(t) = 54.15*tanh(0.1813*t)
+
+function Newton(f, x0, h, eps) {
+    function dfdt(f, x, h) {
+        return (f(x+h) - f(x-h))/(2.0*h);
+    };
+
+    let i = 0;
+    x_n = x0;
+    x_old = x0;
+
+    while (true) {
+        df = dfdt(f, x_n, h);
+        x_old = x_n;
+        x_n = x_n - f(x_n)/df;
+        if (Math.abs(x_n - x_old) < eps) {
+            return {
+                x: x_n,
+                iterations: i+1
+            };
+        }
+        if (i > 10) {
+            return undefined;
+        }
+        i++;
+    }
+}
+
+function f(t) {
+    return 54.16*Math.tanh(0.1813*t) - 100/3.6;
+}
+
+const solution = Newton(f, 2, 0.001, 0.001);
+
+console.log(`t = ${solution.x} in ${solution.iterations} iterations`);