How to select a specific user input from HTML to be used in Javascript

Question

Hi I am trying to build a BAC (Body Alcohol Content) calculator. All of the buttons are single inputs by the user except the "Alcohol Type" which has 3 selections. Check out the HTML below.

 <div class="main-container">
        <div class="viewport">
            <div class="gender-buttons" id="gender-buttons">
                <button class="male-button">MALE</button>
                <button class="female-button">FEMALE</button>
            </div>
            <div class="weight-input" >
                <h3>ENTER WEIGHT</h3>
                <input id="weight-input" type="number" placeholder="75kg" required>
            </div>
            <div class="alcohol-content" >
                <h3>I'VE HAD</h3>
                <input id="alcohol-content" type="number" placeholder="5" required>
            </div>
            <div class="alcohol-type">
                <h3>OF</h3>
                <select name="type-of-alcohol" id="alcohol-type">
                    <option value="1.5">Shots of Spirits</option>
                    <option value="5">Glasses of Wine</option>
                    <option value="12">Pints of Beer</option>
                </select>
            </div>
            <div class="submit-button" >
                <input type="submit" id="submit-button">
            </div>
            <div class="result-container" id="result-container">
                
            </div>
        </div>
    </div>

Here is my code for the JS.

//Inputs

   let weightElement = document.getElementById("weight-input");         // User enters weight
   let amountElement = document.getElementById("alcohol-content")       // Number of drinks consumed
   let submitButton = document.getElementById("submit-button")          // Submits calculation 
   const alcoholTypeElement = document.getElementById("alcohol-type")   // Type of alcohol consumed with ounces as measurement of value 

//Function to calculate BAC

submitButton.addEventListener('click', function(){               // User clicks Submit button will start the calculation
const weight = parseInt(weightElement.value);                    // Weight will be the integer value of the weightElement input
const amount = parseInt(amountElement.value);                    // Amount will be the integer value of amountElement input 
const alcoholType = parseInt(alcoholTypeElement.value);          // AlcoholType will be the integer value of alcoholTypeElement
const gramsOfAlcohol = (alcoholType*amount)*14;                  // 14 is the standard multipler for US/UK for grams of alcohol/ per standard unit
const genderMultiplyer = 0.55;
const bloodAlcoholContent = (gramsOfAlcohol / ((weight * 1000) * genderMultiplyer))*100

document.getElementById("result-container").innerHTML = 
bloodAlcoholContent.toFixed(2);})

As you can see, all of the elements have been linked to their respective JS variables. Now the "Alcohol Type" has 3 selections, Spirits, Wine and Beer. Each with their own values. I'm trying to incorporate the "values" as conditionals in my function.

I have tried creating a switch statement like below to reflect the value at its alcohol volume (For example Spirits is 40% alcohol, and a standard unit is 1.5 ounces, and in the variable above (const gramsOfAlcohol = (alcoholType*amount)*14; where 14 is the standard multiplier to find grams of alcohol per ounce:

    const alcoholTypeValue = (alcoholType) => {

    switch(value){
        case 12:
        return value * 0.05                    // 0.05 = 5% Alcohol (Beers)
        break 
        case 5:
        return value * 0.12                    // 0.12 = 5% Alcohol (Wine)
        break 
        case 1.5:
        return value * 0.4                     // 0.40 = 5% Alcohol (Spirits)
        break 

    }

}

So if the user selects spirits then we know that a standard shot (1.5 ounces) of spirit at 40% alcohol multiplied by 14 will give 8.4 grams of pure alcohol.

So if the user selects wine then we know that a standard glass (5 ounces) of wine at 12% alcohol multiplied by 14 will give 8.4 grams of pure alcohol.

So if the user selects beers then we know that a standard pint (12 ounces) of spirit at 5% alcohol multiplied by 14 will give 8.4 grams of pure alcohol.

I hope this is helpful, I can't seem to find a specific question to my problem but essentially, the selection I end up using needs to be pre-calculated before used in my function.

Thanks

Answer 1

You do not really need a function there, a simple object/dictionary with key/value pairs would do. Also, you need to use parseFloat in parsing the alcohol type, not parseInt as it truncates 1.5 to 1, creating a bug. Also, I did not fix your gender selection as I do not understand how it works:

 let weightElement = document.getElementById("weight-input"); // User enters weight let amountElement = document.getElementById("alcohol-content") // Number of drinks consumed let submitButton = document.getElementById("submit-button") // Submits calculation const alcoholTypeElement = document.getElementById("alcohol-type") // Type of alcohol consumed with ounces as measurement of value submitButton.addEventListener('click', function() { // User clicks Submit button will start the calculation const weight = parseInt(weightElement.value); // Weight will be the integer value of the weightElement input const amount = parseInt(amountElement.value); // Amount will be the integer value of amountElement input // You had a bug here - need to parseFloat, not parseInt const alcoholType = parseFloat(alcoholTypeElement.value); // AlcoholType will be the integer value of alcoholTypeElement // This is your object with key/values pairs const alcoholTypes = { 12: 0.05, 5: 0.12, 1.5: 0.4 } // here you apply your alcohol type multiplicator alcoholTypes[alcoholType] to amount const gramsOfAlcohol = (alcoholTypes[alcoholType] * amount) * 14; // 14 is the standard multipler for US/UK for grams of alcohol/ per standard unit const genderMultiplyer = 0.55; const bloodAlcoholContent = (gramsOfAlcohol / ((weight * 1000) * genderMultiplyer)) * 100 document.getElementById("result-container").innerHTML = bloodAlcoholContent.toFixed(2); })

 <div class="main-container"> <div class="viewport"> <div class="gender-buttons" id="gender-buttons"> <button class="male-button">MALE</button> <button class="female-button">FEMALE</button> </div> <div class="weight-input"> <h3>ENTER WEIGHT</h3> <input id="weight-input" type="number" placeholder="75kg" required> </div> <div class="alcohol-content"> <h3>I'VE HAD</h3> <input id="alcohol-content" type="number" placeholder="5" required> </div> <div class="alcohol-type"> <h3>OF</h3> <select name="type-of-alcohol" id="alcohol-type"> <option value="1.5">Shots of Spirits</option> <option value="5">Glasses of Wine</option> <option value="12">Pints of Beer</option> </select> </div> <div class="submit-button"> <input type="submit" id="submit-button"> </div> <div class="result-container" id="result-container"> </div> </div> </div>