how to select data attribute in html code example

Example 1: css data attribute selector

[data-value] {
  /* Attribute exists */
}

[data-value="foo"] {
  /* Attribute has this exact value */
}

[data-value*="foo"] {
  /* Attribute value contains this value somewhere in it */
}

[data-value~="foo"] {
  /* Attribute has this value in a space-separated list somewhere */
}

[data-value^="foo"] {
  /* Attribute value starts with this */
}

[data-value|="foo"] {
  /* Attribute value starts with this in a dash-separated list */
}

[data-value$="foo"] {
  /* Attribute value ends with this */
}

Example 2: html javascript find data attribute

//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')))