HTML
<form action="#" method="get" id="my_form"> <input type="text" id="my_text"> <button type="submit">資料送出</button> </form>
JS
<script> let my_form = document.getElementById("my_form"); my_form.addEventListener("submit", function(e){ let my_text = document.getElementById("my_text"); if(my_text.value == ""){ e.preventDefault(); alert("需要輸入資料"); } }); </script>
preventDefault()
frontend
jsnote
or
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