如果选中复选框

Question

我希望能够根据选中的复选框更改var chars。

现在，我正在寻找一些复选框是否已经检查过，但是当我尝试它时，密码就会出现空白。

JS代码

function randomString() {
    var chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz=-][';/.,`~!@#$%^&*()_+|}{:?><";
    var string_length = 10;
    var randomstring = '';

    for (var i=0; i<string_length; i++) {
        var rnum = Math.floor(Math.random() * chars.length);
        randomstring += chars.substring(rnum,rnum+1);
    }

    if($('#checkbox1').is(':checked')){
        var lowstring = randomstring.toLowerCase();
        document.randform.randomfield.value = lowstring;
    } else {
        document.randform.randomfield.value = randomstring;
    }

    //  document.randform.randomfield.value = randomstring; //
}

Html代码

<div class="preference">
    <div class="form2">
        <div class="wanted"> <!-- Toggle Special Characters -->
            <label class="input-toggle">
                <input type="checkbox" id="checkbox1" checked>
                <span></span>
            </label>
            <p>Toggle Special Characters</p>
            <div class="wanted"> <!-- Toggle Numbers -->
                <label class="input-toggle">
                    <input type="checkbox" checked>
                    <span></span>
                </label>
                <p>Toggle Numbers</p>
                <div class="wanted"> <!-- Toggle Uppercase -->
                    <label class="input-toggle">
                        <input type="checkbox" checked>
                        <span></span>
                    </label>
                    <p>Toggle Uppercase</p>
                    <div class="wanted"> <!-- Toggle Lowercase -->
                        <label class="input-toggle">
                            <input type="checkbox" checked>
                            <span></span>
                        </label>
                        <p>Toggle Lowercase</p>
                    </div>
                </div>
            </div>
        </div>
    </div>
</div>