change input field value by class name javascript code example

Example 1: javascript element by class

var elementsArray = document.getElementsByClassName("someclassname");

Example 2: how to change input value in javascript using class

// Find the input element with a class of "bar" that is a direct child of a form with a name attribute of "foo"
document.querySelector("form[name='foo'] > input.bar").value = "hehe works"