How to Round to nearest integer in JavaScript [closed]

Question

Hello I'm using JavaScript connected to my html code to make a conversion calculator. What I am having problems on is how to make my result into a rounded integer. I'm new to JavaScript and have tried many attempts to make Math.round(report1) or Math.round(report2) work into my code. Maybe I have to create a separate function? I'm stumped and would appreciate any help for this.

//displaing reported values...for kg to pounds
var report1 = function (kilogram, pound) {
    document.getElementById("result").innerHTML =
        kilogram + "kg = " + pound + "lb";
};


//displaing reported values...for pounds to kilograms
var report2 = function (pound, kilogram) {
    document.getElementById("result").innerHTML =
        pound + "lb = " + kilogram + "kg";
};

//reading in value from lb to kg button
document.getElementById("p_to_kg").onclick = function () {
    var p = document.getElementById("weight").value;
    report2(p, p_to_kg(p));
};

//formula for pounds to kilograms
function p_to_kg(pound_weight) {
    return (pound_weight / 2.2);
}

//reading in value from kg to lb button
document.getElementById("kg_to_p").onclick = function () {
    var kg = document.getElementById("weight").value;
    report1(kg, kg_to_p(kg));
};

//formula for kilograms to pounds
function kg_to_p(kilogram_weight) {
    return (2.2 * kilogram_weight);
}

This is my issue:

Answer 1

HTML input values types are string so to calculate rounded value of them you should convert them to number. there is many ways to convert them to number like call the Number with the string value or adding a plus sign (+) (or division or multiply):

var val = document.querySelector('#val');
var k2l = document.querySelector('#kg-to-lb');
var l2k = document.querySelector('#lb-to-kg');
var res = document.querySelector('#result');

//displaing reported values...for kg to pounds
var report1 = function(kilogram, pound) {
  result.innerHTML =
    kilogram + "kg = " + pound + "lb";
};


//displaing reported values...for pounds to kilograms
var report2 = function(pound, kilogram) {
  result.innerHTML = pound + "lb = " + kilogram + "kg";
};

k2l.addEventListener('click', function(e) {
  var kilogram = val.value;
  var pound = Math.round(kilogram * 2.2);
  report1(kilogram, pound);
});
l2k.addEventListener('click', function(e) {
  var pound = val.value;
  var kilogram = Math.round(pound / 2.2);
  report2(pound, kilogram);
});

value
<input id="val" type="number" />

<button id="kg-to-lb">kg 2 lb</button>
<button id="lb-to-kg">lb 2 kg</button>
<div id="result"></div>

Answer 2

There are three methods of the Math object and one from Number you may use:

var f = 56.14523;

console.log('f: '+f);
console.log('Math.round: '+Math.round(f));
console.log('Math.ceil: '+Math.ceil(f));
console.log('Math.floor: '+Math.floor(f));
console.log('Number.toFixed: '+f.toFixed(2));

The output is:

f: 56.14523

Math.round: 56

Math.ceil: 57

Math.floor: 56

Number.toFixed: 56.15

Math.round will round up to the next integer if the decimal point is .5 or greater.

Math.ceil will always increase the value up to the next integer.

Math.floor will always decrease the value down to the next integer.

Number.toFixed will round to the number of decimal places passed as a parameter.

If you are getting values from inputs, you must first convert them from strings to float values with parseFloat. For example:

function processNumber() {
    var f = document.getElementById("float-input").value;
    f = parseFloat(f);
    if (isNaN(f)) {
        console.log(f+" is not a number");
    } else {
        console.log(f+" rounded is "+Math.round(f));
    }
    return "Temperature: " + Math.round(f) + " degrees";
}

document.getElementById("output-div").textContent = processNumber();