js code to capture input text box content change event_form effects

A guy on the Internet used this method:
readonly: The text box cannot be entered.

<input type="text" id="testId" readonly onpropertychange="showValue(this.value)">
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<script> function dochg(){ document.getElementById("testId").value = "test" } setTimeout("dochg()",1000) function showValue(obj){ alert("changed value is " + obj); } </script>You can use onPropertyChange to capture text Change the event and the experiment is successful!