Derive an array from values of another array

Question

I have this products array in an angular 2 component:

products = [{name: "product1", product_properties: [{name: "color", value: "blue"}, {name: "size", value: "small"}]}, 
            {name: "product2", product_properties: [{name: "color", value: "yellow"}, {name: "size", value: "medium"]}, 
            {name: "product3", product_properties: [{name: "color", value: "green"}, {name: "size", value: "large"}, 
            {name: "product4", product_properties: [{name: "color", value: "green"}, {name: "size", value: "small"}]} 
            {name: "product5", product_properties: [{name: "color", value: "yellow"}, {name: "size", value: "medium"}]

What is the most efficient way to loop over this array and derive an array which looks like the one below using typescript or javascript:

derivedArray = [{property_name: "color", values: ["blue", "yellow", "green"]}, 
                {property_name: "size", values: ["small", "medium", "large"]}]

can you specify what's the the logic of derivedArray ? it's all uniqe values from all products or what ? — shershen
– shershen, Commented May 23, 2016 at 18:58
@shershen I have added products with duplicate product_properties to clarify on expected handling of duplicates. The property_names and their corresponding values should be unique even if the original array has duplicates — Optimus Pette
– Optimus Pette, Commented May 23, 2016 at 20:24

vp_arth · Accepted Answer · 2016-05-23 21:45:26Z

Your array has some syntax errors, I fix them:

var inData = [
  {name: "product1", product_properties:[{name: "color", value: "blue"}, {name: "size", value: "small"} ]}, 
  {name: "product2", product_properties:[{name: "color", value: "yellow"}, {name: "size", value: "medium"}]}, 
  {name: "product3", product_properties:[{name: "color", value: "green"},  {name: "size", value: "large"}]}
];

Let's build hashmap of property => values:

var hash = inData.reduce((acc, p) => {
  p.product_properties.forEach(prop => {
    if (!acc[prop.name]) acc[prop.name] = [];
    if (!~acc[prop.name].indexOf(prop.value)) // filter duplicates
      acc[prop.name].push(prop.value);});
    return acc;
}, {});

And now build requested data structure:

Object.keys(hash).map(key => ({property_name: key, values: hash[key]}))

Result is:

[
  {"property_name":"color","values":["blue","yellow","green"]},     
  {"property_name":"size","values":["small","medium","large"]}
]

user2560539 · Accepted Answer · 2016-05-23 19:33:24Z

Using jQuery

var products = [{name: "product1", product_properties: [{name: "color", value: "blue"}, {name: "size", value: "small"}]}, 
            {name: "product2", product_properties: [{name: "color", value: "yellow"}, {name: "size", value: "medium"}]}, 
            {name: "product3", product_properties: [{name: "color", value: "green"}, {name: "size", value: "large"}]}];
var colorArray = [];
var sizeArray = [];
$.each(products,function(i,v){
var colorAttributes = v.product_properties[0];
var sizeAttributes = v.product_properties[1];
// check if attribute is already passed in the array using jQuery.inArray()
if(colorAttributes.name=="color" && $.inArray(colorAttributes.value,colorArray)==-1){
colorArray.push(colorAttributes.value);
}
if(sizeAttributes.name=="size" && $.inArray(sizeAttributes.value,sizeArray)==-1){
sizeArray.push(sizeAttributes.value);
}
});
var derivedArray = [{property_name: "color", values: colorArray}, 
                {property_name: "size", values: sizeArray}] ;
alert(JSON.stringify(derivedArray ));

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

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