document.querySelectorAll(".row__seat--selected");
Shows a NodeList of 5 elements(<div........>) , I want to take only the "data-tooltip" value in the JSON

function buytickets() {
const tick = document.querySelectorAll(".row__seat--selected");
console.log(tick);
const myJSON = JSON.stringify(tick);
console.log(myJSON);
}
<div class="row">
<div class="row__seat tooltip" data-tooltip="R1"></div>
<div class="row__seat tooltip" data-tooltip="R2"></div>
<div class="row__seat tooltip" data-tooltip="R3"></div>
<div class="row__seat tooltip" data-tooltip="R4"></div>
<div class="row__seat tooltip" data-tooltip="R5"></div>
<div class="row__seat tooltip" data-tooltip="R6"></div>
<div class="row__seat tooltip" data-tooltip="R7"></div>
<div class="row__seat tooltip" data-tooltip="R8"></div>
<div class="row__seat tooltip" data-tooltip="R9"></div>
<div class="row__seat tooltip" data-tooltip="R10"></div>
<div class="row__seat tooltip" data-tooltip="R11"></div>
<div class="row__seat tooltip" data-tooltip="R12"></div>
<div class="row__seat tooltip" data-tooltip="R13"></div>
<div class="row__seat tooltip" data-tooltip="R14"></div>
<div class="row__seat tooltip" data-tooltip="R15"></div>
<div class="row__seat tooltip" data-tooltip="R16"></div>
<div class="row__seat tooltip" data-tooltip="R17"></div>
<div class="row__seat tooltip" data-tooltip="R18"></div>
</div>
you can achieve that by this way
document.querySelectorAll("[data-tooltip]").forEach(el =>{
console.log(el.dataset.tooltip)
})
and to get specific one
console.log(document.querySelector("[data-tooltip='R18']"))