simpsons 1/3 rulee in javascript

index.tsx
function simpsons_1_3_rule(f, a, b, n=2) {
    /* f: function to be integrated
       a: lower limit of integration
       b: upper limit of integration
       n: number of intervals (must be even)
    */
    if (n % 2 == 1) {
        throw new Error('Number of intervals must be even');
    }

    let h = (b - a) / n;

    let sum_odd = 0;
    for (let i = 1; i < n; i += 2) {
        sum_odd += f(a + i * h);
    }

    let sum_even = 0;
    for (let i = 2; i < n-1; i += 2) {
        sum_even += f(a + i * h);
    }

    let integral = (b - a) / (3*n) * (f(a) + 4*sum_odd + 2*sum_even + f(b));
    return integral;
}
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index.tsx
function f(x) { return x**2; }
let a = 0;
let b = 1;
let n = 4;

let integral = simpsons_1_3_rule(f, a, b, n);
console.log(integral);  // Output: 0.3333333333333333
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