<div id="mydiv" data-myval="1992"></div>

var a = $('#mydiv').data('myval'); //getter
$('#mydiv').data('myval',2021); //setter

<div id="mydiv" data-id="1992"></div>

//get data-myval 1992 from mydiv using .attr jQuery
var dataValue = $('#mydiv').attr("data-id");

<div id='your-id'></div>


var id = document.getElementById('your-id');
// 'Setting' data-attributes using setAttribute
id.setAttribute('data-id','7'); // set new value for your id as a 7

// 'Getting' data-attributes using getAttribute
var dataValue = id.getAttribute('data-id'); // get value from data value your-id = '12'

<div id='your-id' data-id='12'></div>

// 'Getting' data-attributes using getAttribute
var id = document.getElementById('your-id');
var dataValue = id.getAttribute('data-id'); // get value from data value your-id = '12'

// 'Setting' data-attributes using setAttribute
id.setAttribute('data-id','7'); // set new value for your id as a 7