如何使用 JavaScript 在特定单选按钮上应用条件

Question

What I want is when I click on specific red id Radio Button then it shows me Alert as you can see in the code... in my case its not happening.. what is the issue and how can I sort this?

 <form> What color do you prefer?<br> <input type="radio" name="colors" id="red">Red<br> <input type="radio" name="colors" id="blue">Blue </form> <script> if (document.getElementById("red").checked == true) { alert('working'); } </script>

Answer 1

You need an eventListener

 document.getElementById("red").addEventListener("change", myAlert); function myAlert() { alert('working'); }

 <form> What color do you prefer?<br> <input type="radio" name="colors" id="red">Red<br> <input type="radio" name="colors" id="blue">Blue </form>

Answer 2

1. You need event listeners - inline event handlers are not recommended
2. You need to decide what you are testing

Here are two ways to running

They are radios so we do not need to test if they are checked

 window.addEventListener("load",function() { // when the page loads // testing clicking the RED only document.getElementById("red").addEventListener("click",function() { console.log("The specific Red event listener was invoked"); }); // delegation document.querySelector("form").addEventListener("click",function(e) { const tgt = e.target; if (tgt.id==="red") console.log("Clicking in the form, we clicked the thing with ID red") }) });

 <form> What color do you prefer?<br> <label><input type="radio" name="colors" id="red">Red</label><br> <label><input type="radio" name="colors" id="blue">Blue</label> </form>

Answer 3

Try like this:

 <form> What color do you prefer?<br> <input type="radio" name="colors" id="red"/>Red<br> <input type="radio" name="colors" id="blue"/>Blue </form> <script> document.getElementById("red").onchange = function() { alert('working'); } </script>

An event handler is needed to run that specific code when a radio button is clicked.