如何在不检查键码的情况下将输入限制为特定值，并且不使值闪烁？

<input type="text" value="特定值" readonly>

<input type="text" id="inputField">

<script>
    var inputField = document.getElementById("inputField");
    var allowedValue = "特定值";

    inputField.addEventListener("keydown", function(event) {
        if (event.key !== allowedValue) {
            event.preventDefault();
        }
    });
</script>

<style>
    #inputField {
        caret-color: transparent;
    }
</style>