How to combine data from an array and object and put together into an array in JavaScript?

I have an array in which I have some string value holding the id along with answer selected and I have different object in which I have the detail about answer which is selected. The below array keep updated whenever we select an option from question.

arr = ["Q1A1", "Q2A3"]

assume Q1 is Question no. 1 and A1 is option selected from the question. And below I have an object for the corresponding Q1 which contained the detail about answers and this object also get change as we move over to Q2

{
id: "Q1",
answers: [
{
id: "Q1A1",
text: "Yes"
},
{
id: "Q1A2",
text: "No"
}  
]
}

same way I have any another object for Q2 if we select the answer in Q1, now we have different object for Q2

{
id: "Q2",
answers: [
{
id: "Q2A1",
text: "Test 1"
},
{
id: "Q2A2",
text: "Test 2"
},
{
id: "Q2A3",
text: "Test 3"
},
{
id: "Q2A4",
text: "Test 4"
}    
]
}

I need to lookup the object with the help of array which contain question and answer(eg, "Q1A1") with selected and need to find the text for answer selected i.e ("Yes") if u look into the above object for question 1. Hence I need put into the array like this way.

result = ["Q1_Yes","Q2_Test3"]

This code will help you to get those results.
<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

let selected = ["Q1A1", "Q2A3"];
let QA = [
  {
id: "Q1",
answers: [
{
id: "Q1A1",
text: "Yes"
},
{
id: "Q1A2",
text: "No"
}  
]
},
{
id: "Q2",
answers: [
{
id: "Q2A1",
text: "Test 1"
},
{
id: "Q2A2",
text: "Test 2"
},
{
id: "Q2A3",
text: "Test 3"
},
{
id: "Q2A4",
text: "Test 4"
}    
]
}
];
let all_answers = QA.reduce((allanswers,qa)=>(qa.answers.map(d=> allanswers[d.id]=[qa.id,d.text]),allanswers),{});

const result = selected.map(selected => all_answers[selected].join('_'))
console.log(result)

<!-- end snippet -->