JSFiddle - React, Tailwind, and code Playground

JavaScript

var array = [4,5,1,9,6],
    max   = 15;

function addRandom(array, max)
{
    if(array.length === max) {
        return array;
    }

    var number = Math.round(Math.random() * (max - 1)) + 1;
    if(array.indexOf(number) === -1) {
        array.push(number);
        return array;
    }
    
    return addRandom(array, max);
}

for(var i = 0; i < 15; i++) {
    addRandom(array, max);
    console.log(array);
}