如何在表单值中存储javascript变量的内容

<input type="hidden" name="variableName" id="hiddenField" value="">
<script>
    var variable = "Hello, World!";
    document.getElementById("hiddenField").value = variable;
</script>

var variable = "Hello, World!";
$.ajax({
    url: "saveVariable.php",
    type: "POST",
    data: { variableName: variable },
    success: function(response) {
        console.log("Variable saved successfully!");
    },
    error: function(xhr, status, error) {
        console.error("Error saving variable: " + error);
    }
});

var variable = "Hello, World!";
document.cookie = "variableName=" + variable;