I would do it like this. The helper functions act directly on the DOM elements, rather than simulating a click.
// an array of elements
const allAccordionElements = Array.from(document.querySelectorAll(".accordion__item"));
const run_code = () => {
// some helper functions
const showTab = (el) => {
el.style.display = "flex";
};
const hideTab = (el) => {
el.style.display = "none";
};
if (allAccordionElements.length > 0) {
// open the first one
showTab(allAccordionElements[0]);
// hide all others
allAccordionElements.slice(1).forEach(thisTab => {
hideTab(thisTab);
});
}
};
document.getElementById('run').addEventListener('click',run_code);.accordion__item {
padding: 0.5em;
margin: 0.5em;
border: 2px dotted green;
background-color: silver;
display: flex;
}<div class="accordion">
<div class="accordion__item">
item one
</div>
<div class="accordion__item">
item two
</div>
<div class="accordion__item">
item three
</div>
</div>
<button id="run">run code</button>