var element = document.querySelector('.element');
var dataAttribute = element.getAttribute('data-name');
// replace "data-name" with your data attribute name
console.log(dataAttribute);//get data-id attribute in plain Javascript
var element = document.getElementById('myDivID');
var dataID = element.getAttribute('data-id');
//get data-id using jQuery
var dataID = $('myDivID').data('data-id');
example <button data-keyname = "a'></button>
let variable = element.dataset.keyname;
or
let varibale = element.['keyname'];
or
let variable = element.getAttribute('data-keyname');//javascript get html data attribute
<button data-id="1" >Click</button>
<button data-id="2" >Click</button>
<button data-id="3" >Click</button>
const btns=document.querySelectorAll('button[data-id]');
[...btns].forEach(btn => console.log(btn.getAttribute('data-id')))document.querySelectorAll('[data-foo]');
// <div id="element" data-name="john"></div>
const el = document.querySelector('#element')
el.dataset.name // 'john'