Tensorflow.js tf.valueAndGrad() Function

// Importing the tensorflow.js library
import * as tf from "@tensorflow/tfjs"

// Initializing a function f(x) = x^2
const f = x => x.square();

// Calling the .valueAndGrad() function over
// the above function as its parameter which
// calculates f'(x) = 2x
const g = tf.valueAndGrad(f);

// Initializing a Tensor of values at which
// value of gradient is calculated
const x = tf.tensor1d([0, 1, 2, 3]);

// Returning the value of f() and 
// gradient of f(x)
const {value, grad} = g(x);

// Getting the value of f()
console.log('value');
value.print();

// Getting the gradient of f(x) at 
// the above tensor values
console.log('grad');
grad.print();

// Importing the tensorflow.js library
import * as tf from "@tensorflow/tfjs"

// Using a function f(x) = x^3 as the parameter
// for the .valueAndGrad() function which
// calculates f'(x) = 3x^2
const g = tf.valueAndGrad(x => x.pow(tf.scalar(3, 'int32')));

// Using a Tensor of values at which
// value of gradient is calculated 
const {value, grad} = g(tf.tensor1d([-1, 0, 0.3, 4]));

// Getting the value of f()
console.log('value');
value.print();

// Getting the gradient of f(x)
console.log('grad');
grad.print();