How can I select the innerhtml of a variable name in an array?

So if I have this code:

const firsthtmlelement = document.getElementById("firsthtmlelement");
const secondhtmlelement = document.getElementById("secondhtmlelement");

const array = ['firsthtmlelement', 'secondhtmlelement']

array[1].innerHTML = "Hello World";

How can I make the secondhtmlelement's innerHTML show up as "Hello World"?

I tried something similar to the code above, when I press something then it is supposed to change the innerHTML of a different element depending on which entry from an array I wanted.

Try to add actual elements in your array instead of just string names:

<!-- begin snippet: js hide: false console: true babel: false -->

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

let firsthtmlelement = document.getElementById("firsthtmlelement");
let secondhtmlelement = document.getElementById("secondhtmlelement");

const button = document.getElementById("button");

const array = [firsthtmlelement, secondhtmlelement];


button.addEventListener("click", function() {
  array[1].innerHTML = "Hello World";
});

<!-- language: lang-html -->

<div id="firsthtmlelement">div1</div>
<div id="secondhtmlelement">div2</div>
<button id="button">press</button>

<!-- end snippet -->

if you variable is a global try using this window["variableName"].innerHTML = myValue;

<!-- begin snippet: js hide: false console: true babel: false -->

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

let firsthtmlelement = document.getElementById("firsthtmlelement");
let secondhtmlelement = document.getElementById("secondhtmlelement");
const button = document.getElementById("button");

const array = ['firsthtmlelement', 'secondhtmlelement'];


button.addEventListener("click", function() {
  console.log(array[1]);
  //in this example we will just hardcode which element to change
  window[array[1]].innerHTML = "Hello World";
});

<!-- language: lang-html -->

<div id="firsthtmlelement">div1</div>
<div id="secondhtmlelement">div2</div>
<button id="button">press</button>

<!-- end snippet -->

When you call arry[1] you are getting a string, and not the variable.

There are many ways to accomplish dynamic variables.

Below I have two solutions:

The first solution creates an object where the key is the name and the value is the querySelector for that element.

The second is using an array like your example.

<!-- begin snippet: js hide: false console: true babel: false -->

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

const elementsObject = {
  "firsthtmlelement": document.querySelector("#firsthtmlelement"),
  "secondhtmlelement": document.querySelector("#secondhtmlelement")
};

elementsObject["firsthtmlelement"].innerHTML = "Hello World 1";

const elementsArray = [document.querySelector("#firsthtmlelement"), document.querySelector("#secondhtmlelement")];

elementsArray[1].innerHTML = "Hello World 2";

<!-- language: lang-html -->

<div id="firsthtmlelement"></div>
<div id="secondhtmlelement"></div>

<!-- end snippet -->