useMemo – Kalkulasi Berat Badan Ideal (Optimisasi Perhitungan)

jsxCopyEditimport React, { useState, useMemo } from 'react';

function IdealWeightCalculator() {
  const [height, setHeight] = useState(170);
  const [weight, setWeight] = useState(65);

  const idealWeight = useMemo(() => {
    console.log('Calculating ideal weight...');
    return (height - 100) - ((height - 100) * 0.1); // rumus Broca
  }, [height]);

  const isIdeal = weight === Math.round(idealWeight);

  return (
    <div>
      <h1>Ideal Weight Checker</h1>
      <div>
        <label>Height (cm): </label>
        <input
          type="number"
          value={height}
          onChange={(e) => setHeight(+e.target.value)}
        />
      </div>
      <div>
        <label>Weight (kg): </label>
        <input
          type="number"
          value={weight}
          onChange={(e) => setWeight(+e.target.value)}
        />
      </div>

      <p>Ideal Weight: {Math.round(idealWeight)} kg</p>
      <p>Status: {isIdeal ? 'Ideal' : 'Belum ideal'}</p>
    </div>
  );
}

• useMemo menyimpan hasil kalkulasi agar tidak dihitung ulang saat render kecuali height berubah.
• Tanpa useMemo, setiap render akan menghitung ulang walau height tidak berubah.
• Cocok untuk kalkulasi berat, data berat, statistik besar, dll.