Question

I would like to rearrange an array of objects in javascript, which looks like this:

[{ year: "1950-12-20", product: ["product 1", "product 2, "product 3"] }, { year: "1951-12-20", product: ["product 3", "product 2"] }, { year: "1952-12-20", product: ["product 3", "product 4"] }]

so that I get two arrays, one with the products and one with the years when they appear.

a = ["product 1", "product 2", "product 3", "product 4"]
b = ["1950-12-20", [ "1950-12-20, "1951-12-20"],["1950-12-20", "1951-12-20", "1952-12-20"],"1952-12-20"]

I have tried to loop through each object through nestled for-loops, but how do I treat the array of strings in the object array in a nice way?

Answer 1

I don’t know what kind of loop you have tested, but this type of code is not so long for what has to be done :

var data = [{ year: "1950-12-20", product: ["product 1", "product 2", "product 3"] }, { year: "1951-12-20", product: ["product 3", "product 2"] }, { year: "1952-12-20", product: ["product 3", "product 4"] }];

var nbData = data.length, iData;
var years = [], products = [], dictProductsYear = {};
var nbProducts, iProduct, p;


// Loop through years
for(iData = 0; iData < nbData; iData ++) {
    products = data[iData].product;
    nbProducts = products.length;

    // Add the current year to the concerned products
    for(iProduct = 0; iProduct < nbProducts; iProduct ++) {
        p = products[iProduct];

        // Registered product
        if(dictProductsYear[p]) dictProductsYear[p].push(data[iData].year);
        // Unregistered one
        else dictProductsYear[p] = [ data[iData].year ];
    }
}

var yearList = [], productList = [];

// Flatten the dictionary in 2 lists
for(p in dictProductsYear) {
    productList.push(p);
    yearList.push(dictProductsYear[p]);
}