JavaScript Forms and Inputs

Written by Swapnil RajaPublished 24 Aug 2026

JavaScript reads and sets form values through the value and checked properties.

Forms are how most pages take information from a visitor.

value is always a string, even for a number input.

Example

javascript

document.body.innerHTML = '<input id="name" value="Ada">';

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

The output is Ada.

Reading Form Values

value holds the current contents of a text, number or select input.

checked is a boolean for checkboxes and radio buttons.

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Example

javascript

document.body.innerHTML = '<input id="agree" type="checkbox" checked>';

const box = document.getElementById("agree");

console.log(box.checked);

box.checked = false;

console.log(box.checked);

Example

javascript

document.body.innerHTML =
  '<select id="size"><option value="s">Small</option>' +
  '<option value="l" selected>Large</option></select>';

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

Example

javascript

document.body.innerHTML = '<input id="name" value="   ">';

const value = document.getElementById("name").value.trim();

console.log(value === "" ? "please enter a name" : value);

Complete Example

html

<!DOCTYPE html>
<html>
<head>
  <title>JavaScript Forms and Inputs</title>
</head>
<body>

  <h1>Forms and Inputs</h1>

  <input id="name" value="Ada">
  <input id="age" type="number" value="36">
  <input id="agree" type="checkbox" checked>

  <p id="out"></p>

  <script>
    const name = document.getElementById("name").value;
    const age = Number(document.getElementById("age").value);
    const agreed = document.getElementById("agree").checked;

    document.getElementById("out").textContent =
      name + " is " + (age + 1) + " next year. Agreed: " + agreed;
  </script>

</body>
</html>

JavaScript Forms and Inputs

Example

Reading Form Values

Syntax

Setting a Value

Example

Numbers Come Back as Strings

Example

Checkboxes

Example

Select Elements

Example

Simple Validation

Example

Complete Example

Try It Yourself

Important Points

Conclusion