如何获取选中的单选按钮的值

Question

I am trying to make a form that is reactive to what a user inputs. I have a list of radio buttons, and for now, I just want to log the value of whatever button is selected in the console (I will implement more logic later). I know I will need some sort of event listener to log the value if a user changes their selection as well.

I am still learning so any explanation with answers is greatly appreciated.

Here is an example of what I have now.

<input type='radio' value='value1' name='example' id='value1'>
<label for='value1'>Value 1</label>
<input type='radio' value='value2' name='example' id='value2'>
<label for='value2'>Value 2</label>
<input type='radio' value='value3' name='example' id='value3'>
<label for='value3'>Value 3</label>

let valueName = document.querySelector('input[name="example"]:checked').value;

When I log valueName to the console. I get a TypeError: Cannot read properties of null (reading 'value'.

Im not sure where to go from here.

Answer 1

To get an immediate value (ie: on DOM ready) you'll need a checked attribute on one of your radio INPUTs.
Then to get the value on change use addEventListener() like ie:

 const getValue = () => document.querySelector('input[name="example"]:checked').value; console.log(getValue()) // Do something on change: document.querySelectorAll('input[name="example"]').forEach(elExample => { elExample.addEventListener("input", () => { console.log(getValue()) }); });

 <label><input type='radio' value='value1' name='example' checked> Value 1</label> <label><input type='radio' value='value2' name='example'> Value 2</label> <label><input type='radio' value='value3' name='example'> Value 3</label>

Answer 2

The reason for your error is because the selector you have specified IS NULL at the point that the code runs.

If you're doing document.querySelector('input[name="example"]:checked').value onload, then the selector doesn't exist because there is no input with name="example" which has the checked attribute. There is however three input elements with name="example" but that isn't what you're telling the JavaScript to select.

To make this function as you intend, then you need to use an event listener as you correctly assumed in your question.

 // Select all inputs with name="example" var radios = document.querySelectorAll("input[name=\"example\"]"); // Use Array.forEach to add an event listener to each radio element. radios.forEach(function(radio) { radio.addEventListener('change', function() { let valueName = document.querySelector('input[name="example"]:checked').value; console.log(valueName) }) });

 <input type='radio' value='value1' name='example' id='value1'> <label for='value1'>Value 1</label> <input type='radio' value='value2' name='example' id='value2'> <label for='value2'>Value 2</label> <input type='radio' value='value3' name='example' id='value3'> <label for='value3'>Value 3</label>