Can't use variable from previous function in new function or syntax?

Question

I'm rather new to Javascript, and I'm trying to calculate the BMR in "Oppgave A" of a male who is 18 years old and 180 centimeters high. The first function of the calculation works. I get the amount of calories this male with a user-defined weight needs each hour.

Problem: When trying to calculate the energy used in sitting at the desk bmr * 1.2, the previous variable bmr i used in the function printBmr from the function turns out is undefined when I call it in the new function printPalStille.

Question: How can I use the variable bmr from the previous function printBmr and use it in the new function *printPalStille *under the new variabel pal?

The Code:

<script>
     // __________________________________________________

    // Oppgave A
    var vekt = document.getElementById("idtxtVekt");
    var svar = document.getElementById("idpSvar");
    vekt.focus();


    vekt.addEventListener("keyup", printBmr);
    function printBmr (event) {
        if (event.keyCode === 13) {
        var kalkuler = 35.27 + (0.558 * vekt.value);
        var bmr = Math.floor(kalkuler);
        svar.innerHTML="Energimengden som kreves hver time for deg er: " + bmr + " kalorier i timen.";
        }


    }

    // __________________________________________________



    // Oppgave B
    var palStille = document.getElementById("idbtnStille");
    var palTur = document.getElementById("idbtnTur");
    var svarPal = document.getElementById("idpsvarPal");
    palStille.addEventListener("click", printPalStille);
    // palTur.addEventListener("click", printPalTur);

    function printPalStille (event) {
        var pal = bmr.value * 1.2;
        svarPal.innerHTML = "Din pal er: " + pal.value;
        console.log(bmr);
        }



     // __________________________________________________
</script>

I am a complete beginner and I'm trying to improve my javascript skills, but sometimes things get too complicated for me to understand within forums and communities, therefore I have problems troubleshooting this from other questions, even though the answer is there, and i apologise for the use of Norwegian phrases and words with-in my code :(

DedaDev · Accepted Answer · 2018-09-23 19:43:42Z

2

There are many ways, simplest would be to initiate bmr variable above function instead of in a function.

var bmr;
function printBmr (event) {
    if (event.keyCode === 13) {
    var kalkuler = 35.27 + (0.558 * vekt.value);
    bmr = Math.floor(kalkuler);
    svar.innerHTML="Energimengden som kreves hver time for deg er: " + bmr + " kalorier i timen.";
    }
}

now after function is triggered bmr will hold Math.floor(kalkuler) value, and you can access it globaly.

answered Sep 23, 2018 at 19:43

DedaDev

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Comments

KusokBanana · Accepted Answer · 2018-09-23 19:42:13Z

2

Please, read about global and local variables in JavaScript

You could:

1) Return this value from another function (wrap this math calc into function and call it directly for variables) [Recommend this]

2) Declare this variable as global (out of all functions)

3) Push it as function parameter

answered Sep 23, 2018 at 19:42

KusokBanana

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Comments

ThS · Accepted Answer · 2018-09-23 20:02:07Z

As a short answer for your issue, you can declare the bmr variable as global. Furthermore, your making some mistakes in your code, you wrote pal.value, bmr.value and that's wrong, to get a variable's value you'll only need to call it using its name like: var something = somethingElse * 2.

Here's a working demo for you:

// notice the bmr variable, it's declared as global.
// it's recommended to declare all the variable at the beginning.
var vekt = document.getElementById("idtxtVekt"),
svar = document.getElementById("idpSvar"),
bmr = 0,
palStille = document.getElementById("idbtnStille"),
palTur = document.getElementById("idbtnTur"),
svarPal = document.getElementById("idpsvarPal");

vekt.focus();
vekt.addEventListener("keyup", printBmr);
palStille.addEventListener("click", printPalStille);

// functions
function printBmr (event) {
  if (event.keyCode === 13) {
var kalkuler = 35.27 + (0.558 * vekt.value);
bmr = Math.floor(kalkuler);
svar.textContent = "Energimengden som kreves hver time for deg er: " + bmr + " kalorier i timen.";
  }
}
function printPalStille (event) {
  var pal = bmr * 1.2;
  svarPal.textContent = "Din pal er: " + pal;
  console.log(pal);
}

<div id="boksEn" style="background-color: tomato; color: white; padding: 5px 5px;">
<h1>1. BMR</h1>
<p><b>BMR</b> er Energimengden som kreves for at organene våre skal fungere, og er avhengig av kjønn, alder, høyde og vekt.</p>
<p>Regn ut BMR for gutt 18 år og 180cm høy: </p>
<p>Tast inn vekt i kg: <input type="number" id="idtxtVekt"></p>
<p id="idpSvar">Svar: </p>
</div>
<div id="boksTo">
<h1>2. PAL</h1>
<p><b>PAL</b> er et uttrykk for ulike typer aktivitet, som for eksempel å sitte stille eller å gå en tur.</p>
<p>Velg én aktivitet for å finne ut av energiforbruk: </p>
<button id="idbtnStille">Stille sitting</button>
<button id="idbtnTur">Tur gående</button>
<p id="idpsvarPal">Svar: </p>
</div>

I used textContent attribute instead of the innerHTML one as we're just appending some text and not HTML.

This actually answered my followup question to this, as like you mentioned the ".value" ending is undefined. So theres no reason to have ".value", and I thank you so much for being very patient with me and helping me understand the errors in my code :D!

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