​x
 
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<!DOCTYPE html>
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<title>My Example</title>
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​
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<script>
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// Wait for DOM to load
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document.addEventListener("DOMContentLoaded", function(event) {
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​
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  // Put the button into a variable
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  var e = document.getElementById("myForm");
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  // Wait for user to click the button
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  e.addEventListener( "change", function() {
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    // Put the selected value into a variable
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    var myColor = this.color.value;
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    // The "If" statement. Only display the alert if "Blue" was selected.
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    if (myColor == "Blue") {
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      // Output a message
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      document.getElementById("msg").innerHTML = "Just like the sky!";
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    }
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  }, false);
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});
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</script>
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​
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<!-- Replace '{action page}' with your own action page to support non-JavaScript users -->
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<form id="myForm" name="myForm" action="{action page}">
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  <label>
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    <input type="radio" name="color" value="Blue"> Blue
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  </label>
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  <label>
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    <input type="radio" name="color" value="Red"> Red
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  </label>
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  <label>
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    <input type="radio" name="color" value="Green"> Green
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  </label>
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</form>
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​
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<p id="msg"></p>