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<html><body><form action="/action_page.php"> Zip code: <input type="text" id="myText" name="zip_code"> <input type="submit"></form><p>Click the "Try it" button to specify a regular expression that the text field's value will be checked against. Note that we also set the "title" to describe the pattern.</p><button onclick="myFunction()">Try it</button><p id="demo"></p><script>function myFunction() { document.getElementById("myText").pattern = "[1-3]"; document.getElementById("myText").title = "A number from 1 to 3"; document.getElementById("demo").innerHTML = "The text field can now only contain numbers from 1 to 3.";}</script></body></html>