jQuery 顯示/隱藏選項，如果第一個選擇，默認顯示第二個選擇的選項

Question

如果我選擇了3 列，我想獲得默認值 -布局 4

selected="selected"這僅適用於column_select但不適用於第二個layout_select表單。

我應該在代碼中添加或更改什么/在哪里？

 $(document).ready(function() { var optarray = $("#layout_select").children('option').map(function() { return { "value": this.value, "option": "<option value='" + this.value + "'>" + this.text + "</option>" } }) $("#column_select").change(function() { $("#layout_select").children('option').remove(); var addoptarr = []; for (i = 0; i < optarray.length; i++) { if (optarray[i].value.indexOf($(this).val()) > -1) { addoptarr.push(optarray[i].option); } } $("#layout_select").html(addoptarr.join('')) }).change(); })

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <select name="column_select" id="column_select"> <option value="col1">1 column</option> <option value="col2">2 column</option> <option value="col3">3 column</option> </select> <select name="layout_select" id="layout_select"> <!--Below shows when '1 column' is selected is hidden otherwise--> <option value="col1">none</option> <!--Below shows when '2 column' is selected is hidden otherwise--> <option value="col2_ms">layout 1</option> <option value="col2_sm">layout 2</option> <!--Below shows when '3 column' is selected is hidden otherwise--> <option value="col3_mss">layout 3</option> <option value="col3_ssm" selected="selected">layout 4</option> <option value="col3_sms">layout 5</option> </select>

Answer 1

https://codepen.io/phong18/pen/aboLdGG更新你的 js：

$(document).ready(function() {
    var optarray = $("#layout_select").children('option').map(function() {
        var selected = '';
        if($(this).attr('selected')){
            selected = "selected='"+ $(this).attr('selected')+"'";
        }
        return {
            "value": this.value,
            "option": "<option value='" + this.value + "' "+selected+" >" + this.text + "</option>"
        }
    })

    $("#column_select").change(function() {
        $("#layout_select").children('option').remove();
        var addoptarr = [];
        for (i = 0; i < optarray.length; i++) {
            if (optarray[i].value.indexOf($(this).val()) > -1) {
                addoptarr.push(optarray[i].option);
            }
        }
        $("#layout_select").html(addoptarr.join(''))
    }).change();
})

Answer 2

也保存選擇的狀態

 $(document).ready(function() { var optarray = $("#layout_select").children('option').map(function() { return { "value": this.value, "option": `<option value="$(this.value}"${this.defaultSelected?" selected":""}>${this.text}</option>`, } }) $("#column_select").change(function() { $("#layout_select").children('option').remove(); var addoptarr = []; for (i = 0; i < optarray.length; i++) { if (optarray[i].value.indexOf($(this).val()) > -1) { addoptarr.push(optarray[i].option); } } $("#layout_select").html(addoptarr.join('')) }).change(); })

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <select name="column_select" id="column_select"> <option value="col1">1 column</option> <option value="col2">2 column</option> <option value="col3">3 column</option> </select> <select name="layout_select" id="layout_select"> <!--Below shows when '1 column' is selected is hidden otherwise--> <option value="col1">none</option> <!--Below shows when '2 column' is selected is hidden otherwise--> <option value="col2_ms">layout 1</option> <option value="col2_sm">layout 2</option> <!--Below shows when '3 column' is selected is hidden otherwise--> <option value="col3_mss">layout 3</option> <option value="col3_ssm" selected="selected">layout 4</option> <option value="col3_sms">layout 5</option> </select>

Answer 3

使用clone()和filter()更簡單方法。

您在頁面加載時存儲一組克隆的選項。 對於每個更改，您再次克隆該存儲集並根據所選值對其進行過濾。

 var $clonedOpts = $("#layout_select").children().clone(); $("#column_select").change(function() { var $layOpts = $clonedOpts.clone().filter('[value^=' + $(this).val() + ']'); $("#layout_select").html($layOpts); }).change();

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <select name="column_select" id="column_select"> <option value="col1">1 column</option> <option value="col2">2 column</option> <option value="col3">3 column</option> </select> <select name="layout_select" id="layout_select"> <!--Below shows when '1 column' is selected is hidden otherwise--> <option value="col1">none</option> <!--Below shows when '2 column' is selected is hidden otherwise--> <option value="col2_ms">layout 1</option> <option value="col2_sm">layout 2</option> <!--Below shows when '3 column' is selected is hidden otherwise--> <option value="col3_mss">layout 3</option> <option value="col3_ssm" selected="selected">layout 4</option> <option value="col3_sms">layout 5</option> </select>