如果选中单选按钮如何读取并使用javascript将其保存为1？

I have 3 radio buttons:

我有3个单选按钮：

<div id="step-1">
    <h2 class="StepTitle">
        <label style="font-weight: bold; color: #662819;" id="frage1"></label>
    </h2>
    <br />

    <input type="radio" name="group1" id="antwort1" value="" onmousedown="this.__chk = this.checked" onclick="if (this.__chk) this.checked = false" />
    <label id="antwort1fuerFrage1"></label>
    <br />
    <br />

    <input type="radio" name="group1" id="antwort2" value="" onmousedown="this.__chk = this.checked" onclick="if (this.__chk) this.checked = false" />
    <label id="antwort2fuerFrage1"></label>
    <br />
    <br />

    <input type="radio" name="group1" id="antwort3" value="" onmousedown="this.__chk = this.checked" onclick="if (this.__chk) this.checked = false" />
    <label id="antwort3fuerFrage1"></label>
</div>
<div id="