JavaScript : switch and check radio button - Stack Overflow

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I wrote this code to switch between radio buttons and show my custom alert.

<script>
    function test() {
            if (radio[0].checked = true) {
                alert("hello1");
            }

            if (radio[1].checked = true) {
                alert("hello2");
            }
    }
</script>


<input type="radio" onclick="test()" value="0">
<input type="radio" onclick="test()" value="1">

When check any of radio buttons it must show specific alert. What is wrong?

I wrote this code to switch between radio buttons and show my custom alert.

<script>
    function test() {
            if (radio[0].checked = true) {
                alert("hello1");
            }

            if (radio[1].checked = true) {
                alert("hello2");
            }
    }
</script>


<input type="radio" onclick="test()" value="0">
<input type="radio" onclick="test()" value="1">

When check any of radio buttons it must show specific alert. What is wrong?

• javascript
• radio-button

Share Improve this question Follow asked Oct 31, 2011 at 15:01 MortezaMorteza 2,15388 gold badges3838 silver badges6262 bronze badges

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3 Answers 3

Sorted by: Reset to default 3

You should name your radio buttons, and call them from javascript.

<script>
    function test() {
        if (document.getElementById('radio1').checked == true) {
            alert("hello1");
        }

        if (document.getElementById('radio2').checked == true) {
            alert("hello2");
        }
    }
</script>


<input type="radio" id="radio1" onclick="test()" value="0">
<input type="radio" id="radio2" onclick="test()" value="1">

Two things you need to take note here: 1) You must use the 'name' attribute in the radio button. Otherwise you won't be able to check the radio button. 2) You cannot use radio[0] to point to the radio button. You can assign an ID to it and use getElementById method to use it in Javascript. Another easy way is to pass the object to the function. Please refer to the sample code below:

<script>
    function test(radioObj) {
        if(radioObj.value == "0")
            alert("Hello1");
        else if (radioObj.value == "1")
            alert("Hello2");
    }
</script>

<input type="radio" name="test" onclick="test(this)" value="0">
<input type="radio" name="test" onclick="test(this)" value="1">

radio[0] and radio[1] are defined in your html but not in your javascript. You can try using JQuery or one of the many javascript selector libraries. Or use getElementById

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