javascript - Change radio button value to the value of text input

I have this code which has a radio button. I want to get the value of the text box and set it as the value of the selected radio button.

HTML

onsubmit="return formValidation();">
    Monthly amount of
    P
    300.00
    P
        "text" value="">(please specify)
    

Javascript

window.onload = function() {
    var promised = document.getElementsByName("amounts");
    for (var i = 0; i < promised.length; i++) {
        promised[i].onclick = function() {

            var rads = this.form[this.name];
            for (var i = 0; i < rads.length; i++) {
                var textField = this.form[rads[i].value.toLowerCase() + "Amount"];
                if (textField) textField.disabled = !rads[i].checked;
            }
        }
    }
}