如何从Javascript中的嵌套数组中获取10个非重复随机对象？

Question

I have an object like this:

var database = [
  {
    category: 'CPUs',
    id: 1,
    products: [Product, Product, Product] //Product is an object
  },
  {
    category: 'GPUs',
    id: 2,
    products: [Product, Product]
  }      
];

and so on..

I'd like to get 10 random products in total, non-repeating. There can be more than one from the same category, as long as they are different products. How can I do this? I tried this:

function getRandomFromObject(){
    var productsCollected = [];

    while(productsCollected.length < 10){
        var randomCategory = database[Math.floor(Math.random()*database.length)];
        var randomProduct = randomCategory.products[Math.floor(Math.random()*randomCategory.products.length)];
        productsCollected.push(randomProduct);
    }
    return productsCollected;
}

Answer 1

Things become easier if you first concatenate all the products into one array, then shuffle that array and finally take the first 10 from that:

 function shuffle(a) { for (let i = a.length; i; i--) { let j = Math.floor(Math.random() * i); [a[i - 1], a[j]] = [a[j], a[i - 1]]; } return a; } function getRandomFromObject(count){ return shuffle([].concat(...database.map(o => o.products))).slice(0, count); } var database = [ { category: 'CPUs', id: 1, products: ['a', 'b', 'c'] //Product is an object }, { category: 'GPUs', id: 2, products: ['d', 'e'] }, { category: 'GPUs', id: 3, products: ['f', 'g', 'h', 'i', 'j'] } ]; console.log(getRandomFromObject(10).join(',')); 

Addendum: If you can have the same Product object occurring in different categories, then apply a Set to the concatenated array, so to eliminate these duplicates:

return shuffle([...new Set([].concat(...database.map(o => o.products)))]).slice(0, count);

ES5 Code

As you asked in comments for ES5, and the need to consider products with the same ISBN property as the same products, here is the code for that:

 function shuffle(a) { for (var i = a.length; i; i--) { var j = Math.floor(Math.random() * i); var temp = a[i - 1]; a[i - 1] = a[j]; a[j] = temp; } return a; } function getRandomFromObject(count){ var uniq = {}; // Unique list of products, keyed by ISBN database.forEach(function (o) { o.products.forEach(function (product) { uniq[product.isbn] = product; }); }); var products = []; for (product in uniq) { products.push(uniq[product]); } return shuffle(products).slice(0, count); } var database = [ { category: 'CPUs', id: 1, products: [{ isbn: 'a' }, { isbn: 'b' }, { isbn: 'c' }] //Product is an object }, { category: 'GPUs', id: 2, products: [{ isbn: 'd' }, { isbn: 'a' }, { isbn: 'j' }] // has same isbn as in CPUs }, { category: 'Others', id: 3, products: [{ isbn: 'e' }, { isbn: 'f' }, { isbn: 'g' }, { isbn: 'h' }, { isbn: 'i' }] } ]; console.log(getRandomFromObject(10));