javascript find select option index based on option text

I am trying (and failing) to check if an option exists in the select element, based on the option’s text:

<select id="select">

    <option value="13">I1</option>
    <option value="23">I21</option>
    <option value="954">I33</option>

</select>

var select = document.getElementById('select');

findInvoice(44);

function findInvoice(value_option) {
    
    let x = select.value = [...select.options].findIndex(option => option.text === 'I' + value_option);
    console.log(x);
    
}

This does output the -1 value for the index, but it also sets the option index in the select form as well. I strictly only want to check if the index exists or not without selecting it.

>Solution :

You need to remove select.value when assign value to x

Change:

let x = select.value = [...select.options].findIndex(option => option.text === 'I' + value_option);

to:

let x = [...select.options].findIndex(option => option.text === 'I' + value_option);

var select = document.getElementById('select');

findInvoice(44);

function findInvoice(value_option) {
    
    let x =  [...select.options].findIndex(option => option.text === 'I' + value_option);
    console.log(x);
    
}

<select id="select">

    <option value="13">I1</option>
    <option value="23">I21</option>
    <option value="954">I33</option>

</select>