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Accepted
Eduardo Sebastian
Asked: 2020-01-16 19:08:57 +0800 CST 2020-01-16 19:08:57 +0800 CST

How to get a random number with decimals and integers in JavaScript?

  • 772

I can get random numbers in a custom range, with:

Math.floor(Math.random() * ( maximo - minimo + 1 ) + minimo )

Example:

var max = 10,
    min = 4,
    random = Math.floor(Math.random() * (max - min + 1) + min);
    
    console.log(random);

But how can I get numbers between a certain range, including decimals between them?

For example, I want to get the numbers 1 - 3 , and the first decimal included, the options would be:

[1, 1.1, 1.2, 1.3 .... 3] ,

How can I do it in JavaScript?

javascript

2 Answers

  1. Best Answer

    Think of it this way: a random between 4 and 10 to 1 decimal would be the same as one between 40 and 100, divided by 10, right? ... Well, generalizing:

    //Aleatorio entre min y max (incluyendo a max) con n decimales
//
function aleatorio(minimo, maximo, decimales) {
    var precision = Math.pow(10, decimales);
    minimo = minimo*precision;
    maximo = maximo*precision;
    return Math.floor(Math.random()*(maximo-minimo+1) + minimo) / precision;
}


    demonstration:

    function aleatorio(minimo, maximo, decimales) {
    var precision = Math.pow(10, decimales);
    minimo = minimo*precision;
    maximo = maximo*precision;
    
    return Math.floor(Math.random()*(maximo-minimo+1) + minimo) / precision;
}


//Calcular
document.getElementById("calc")
    .addEventListener(
        "click",
        function (event) {
            var min = document.getElementById("min").value,
                max = document.getElementById("max").value,
                decimales = document.getElementById("decimales").value,
                resultado = document.getElementById("resultado");
            
            resultado.innerText = aleatorio(min,max,decimales);
        }
    );
    input {
    width: 100%;
}
    Min:
<input id="min" type="number" value="1">
Max:
<input id="max" type="number" value="3">
Decimales:
<input id="decimales" type="number" value="1">
<input id="calc" type="button" value="Calcular">
Aleatorio:
<pre id="resultado" />

    • 6

  2. The main thing would be to remove the floorso you avoid truncating the decimal and avoid returning only an integer remove the +1to avoid taking values ​​greater than the maximum number passed,

    var max = 3,
min = 1 ,
//Retorna un número aleatorio entre min (incluido) y max (excluido)
random = Math.random() * (max - min) + min;
console.log(random);

    If you want to limit the number of decimal places you can always fall back to toFixed, (2 for the example)

    var max = 3,
min = 1 ,
random = (Math.random() * (max - min) + min).toFixed(2);
console.log(random);

    • 5