SOURCE

function radio_change(){
    var radio1 = document.getElementById('radio1');
    var radio2 = document.getElementById('radio2');
    var text = document.getElementById('text');
    if(radio1.checked){
        text.disabled = '';
    }else{
        text.value = "";
        text.disabled = "disabled";
    }


}

<input type="radio" id="radio1" name="radio" onchange="radio_change()">可用
<input type="radio" id="radio2" name="radio" onchange="radio_change()">不可用
<input type="text" id="text" disabled>

input[type="text"]:enabled{
    background: gold
}
input[type="text"]:disabled{
    background: dimgray
}