JSON object restructure using ES6 [duplicate]

You can use reduce to group the array into one object. Use Object.values to convert the object into an array.

let tires = [{"name":"fancyProduct1","quantity":1},{"name":"fancyProduct1","quantity":1},{"name":"fancyProduct1","quantity":1},{"name":"fancyProduct2","quantity":1}];

let result = Object.values(tires.reduce((c, {name,quantity}) => {
  c[name] = c[name] || {name,quantity: 0}
  c[name].quantity += quantity;
  return c;
}, {}));

console.log(result);

Using Reduce will accomplish this:

var products = { tires: [ {name: "fancyProduct1", quantity: 1}, {name: "fancyProduct1", quantity: 1}, {name: "fancyProduct1", quantity: 1}, {name: "fancyProduct2", quantity: 1}] };

var result = products.tires.reduce((acc,current) => {

    if (!acc[current.name]) {
       acc[current.name] = { name: current.name, quantity: 0};
    }

    acc[current.name].quantity++;

    return acc;
}, {});

var resultArray = Object.values(result);
console.log(resultArray);

Well you can use a simple Array.forEach() call to loop over the array items, along with Array.find() to check for the existence of your iterated item in the result array and do your logic accordingly.

This is how should be your code:

var result = [];

tires.forEach(function(el) {
  let found = result.find(o => o.name === el.name);
  if (found) {
    found["quantity"] += el["quantity"];
  } else {
    result.push(el);
  }
});

Demo:

var tires = [{
  name: "fancyProduct1",
  quantity: 1
}, {
  name: "fancyProduct1",
  quantity: 1
}, {
  name: "fancyProduct1",
  quantity: 1
}, {
  name: "fancyProduct2",
  quantity: 1
}];

var result = [];

tires.forEach(function(el) {
  let found = result.find(o => o.name === el.name);
  if (found) {
    found["quantity"] += el["quantity"];
  } else {
    result.push(el);
  }
});

console.log(result);

You can do something like this...

var newTries = tires.map(n => (
 // logic for new array where you can get attributes of item in tires to create a new array. 
console.log(n);  // this can show what properties are available in the current item write it to the console. 
)};

Hope this helps.