Following is the code to autofill a field in JavaScript same as another −
Example
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
body {
font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}
input {
padding: 5px;
margin: 5px;
display: block;
}
button {
padding: 3px;
}
</style>
</head>
<body>
<h1>Autofill a filled textbox same as another</h1>
<input type="text" class="addr" placeholder="address" />
<button class="Btn">Same as above</button>
<input type="text" class="addr" placeholder="address" />
<script>
let BtnEle = document.querySelector(".Btn");
let addrEle = document.querySelectorAll(".addr");
BtnEle.addEventListener("click", () => {
addrEle[1].value = addrEle[0].value;
});
</script>
</body>
</html>Output
On typing the address in first text box −
On clicking the ‘Same as above’ button −