JSFiddle - React, Tailwind, and code Playground

JavaScript

var data = {
"Nike": [
    {
    "id": "1",
    "name": "test",
    "myimage": "image.gif"},

     {
    "id": "2",
    "name": "test",
    "myimage": "image.gif"}
],

"Adidas": [
    {
    "id": "3",
    "name": "Football Boots",
    "myimage": "image.gif"},

     {
    "id": "4",
    "name": "Running Shoes",
    "myimage": "image.gif"}
]
}

var mashed = Object.keys(data).reduce(function(arr, key) {
    return arr.concat(data[key]);
}, []);

console.log(mashed);