This should be one possible way to obtain the desired objective.

Code Snippet

let arr = [ 
    {tags: {x: 2, y: 12}}, 
    {type: {x: 23, y: 44}}, 
    {order: {x: 5, y: 1200}}, 
];

const res = arr.flatMap(
  obj => Object.entries(obj).map(
    ([k, {x}]) => ({ [k]: x })
  )
);

console.log(res);

Explanation

• Iterate over the array using .flatMap() (to avoid nested-array in the result)
• Take each object (obj) and iterate over key-value pairs using Object.entries()
• Now, de-structure the [key, value] iterator to directly access prop x
• Transform it to an object with x as the value

let arr = [ 
    {tags: {x: 2, y: 12}}, 
    {type: {x: 23, y: 44}}, 
    {order: {x: 5, y: 1200}}, 
]

arr.map((item) => {
    const newItem = {}
    newItem[ Object.keys(item)[0]] = item[Object.keys(item)[0]].x
    return newItem
})

This is my solution. It's worked but I don't think it is good answer!

You're moving in the right direction. You just need Object.entries to help you get k and v as an array [k, v].

let arr = [ {tags: {x: 2, y: 12}}, {type: {x: 23, y: 44}}, {order: {x: 5, y: 1200}} ];

const output = arr.flatMap(
  o => Object.entries(o).map(([k,v]) => ({[k]:v.x}))
);
console.log( output );

Alternatively, since v has the same properties in all the elements, you can use destructuring as in the demo below:

let arr = [ {tags: {x: 2, y: 12}}, {type: {x: 23, y: 44}}, {order: {x: 5, y: 1200}} ];

const output = arr.flatMap(
  o => Object.entries(o).map(([k,{x,y}]) => ({[k]:x}))
);
console.log( output );