JSFiddle - React, Tailwind, and code Playground

by guydog28

HTML

<div class="container">
    <header>
        <h1>Weight Forecast Calculator</h1>
    </header>
    <div id="description">
      <p><strong>This form is for estimating how caloric intake and exercise (or lack thereof) will affect your weight over time</strong></p>

      <p>Modify the values in the form below and watch how the results change under it.</p>

      <p><strong>Notes:</strong></p>

      <ul>
        <li>For multiplier, choose an estimated value based on these:
          <ul>
            <li>Sedentary (little or no exercise): <strong>1.2</strong>
              <ul>
                <li>This level might apply to someone who does light activity for daily living but does not engage in any formal exercise and may have a desk job.</li>
              </ul>
            </li>
            <li>Lightly active (light exercise/sports 1-3 days/week): <strong>1.375</strong>
              <ul>
                <li>This could be someone who does a little light exercise, such as walking or gentle yoga, a few times a week.</li>
              </ul>
            </li>
            <li>Moderately active (moderate exercise/sports 3-5 days/week): <strong>1.55</strong>
              <ul>
                <li>This level would apply to someone who engages in moderate activity like brisk walking, dancing, swimming, or cycling most days of the week.</li>
              </ul>
            </li>
            <li>Very active (hard exercise/sports 6-7 days a week): <strong>1.725</strong>
              <ul>
                <li>This would be someone who does more intense exercise like running, fast cycling, or competitive sports almost every day.</li>
              </ul>
            </li>
            <li>Extra active (very hard exercise/sports & a physical job or 2x training): <strong>1.9</strong>
              <ul>
                <li>This level would apply to someone who does intense physical exercise multiple times a day or has a physically demanding job, like construction work or...

CSS

body {
    font-family: Arial, sans-serif;
    background-color: #f5f5f5;
    padding: 20px;
    color: #333;
}

.container {
    background-color: #fff;
    max-width: 700px;
    margin: auto;
    padding: 20px;
    border-radius: 5px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    overflow: hidden;
}

.container h1 {
    text-align: center;
    margin-bottom: 40px;
    color: #333;
}

.row {
    display: flex;
    flex-wrap: wrap;
    margin-bottom: 15px;
    justify-content: space-between;
}

.inputGroup {
    flex: 1;
    padding: 0 10px;
    margin-bottom: 20px;
}

.inputGroup label {
    display: block;
    font-weight: bold;
    margin-bottom: 10px;
}

.inputGroup input,
.inputGroup select {
    width: 100%;
    padding: 8px;
    border-radius: 5px;
    border: 1px solid #ddd;
    font-size: 14px;
}

.inputGroup input:focus,
.inputGroup select:focus {
    outline: none;
    border-color: #aaa;
}

#results {
    margin-top: 30px;
    padding: 20px;
    background-color: #f0f0f0;
    border-radius: 5px;
    display: none;
}

.output {
    font-size: 16px;
    font-weight: normal;
}

#calculate {
    width: 100%;
    padding: 10px;
    border: none;
    border-radius: 5px;
    background-color: #28a745;
    color: white;
    font-size: 16px;
    cursor: pointer;
    margin-top: 20px;
}

#calculate:hover {
    background-color: #218838;
}

#calculate:focus {
    outline: none;
}

.description {
    margin-bottom: 20px;
    line-height: 1.6;
    color: #555;
}

JavaScript

document.addEventListener('DOMContentLoaded', function () {
    document.getElementById('startDateInput').valueAsDate = new Date();
    document.getElementById('calculate').addEventListener('click', function() {
    		const startDate = new Date(document.getElementById('startDateInput').value);
        // Get values from the form
        const sex = document.getElementById('sexInput').value;
        const birthday = new Date(document.getElementById('birthdayInput').value);
        const heightFt = parseInt(document.getElementById('heightFtInput').value);
        const heightIn = parseFloat(document.getElementById('heightInInput').value);
        const weight = parseFloat(document.getElementById('weightInput').value);
        const calories = parseInt(document.getElementById('caloriesInput').value);
        const multiplier = parseFloat(document.getElementById('multiplierInput').value);
        const outputDays = parseInt(document.getElementById('outputDaysInput').value);
        const forecastDays = parseInt(document.getElementById('forecastDaysInput').value);

        const ageNow = (startDate-birthday)/(1000*60*60*24*365);


        // Convert height to centimeters
        const heightCm = (heightFt * 12 + heightIn) * 2.54;

        // Convert weight to kilograms
        let currentWeightKg = weight * 0.453592; // let, because this will change

        // Prepare results output
        let resultsOutput = '';

        // Loop through each day
        for(let days = 1; days <= forecastDays; days++) {
            // Calculate the age incrementally for each day
            const age = ageNow + days / 365; // This assumes a year is always 365 days
            
            // Calculate current TDEE
            const tdee = multiplier * (10 * currentWeightKg + 6.25 * heightCm - 5 * age + (sex === 'female' ? -161 : 5));
            
            // Calculate weight change for the day, in kg
            const weightChangeKg = (calories - tdee) / 7700; // 1 kg is approx....