get the value of an input form element (input value)

console.log(document.getElementById("my_input").value);

HTML

<input type="text" value="my value" id="my_input">
<button onclick="get_input_val();" class='btn btn-primary'>Get Input Value</button>

Javascript

// let my_input_val = document.getElementById("my_input").value;
// var my_input_val = document.getElementById("my_input").value;
// console.log(my_input_val);

function get_input_val() {
  var my_input_val = document.getElementById("my_input").value;
  alert(my_input_val);
}

document.addEventListener("DOMContentLoaded", function(event) { 
	var my_input_val = document.getElementById("my_input").value;
	console.log(my_input_val);
});