如何驗證選擇的多選下拉查詢的長度

Question

我正在研究 jQuery Chosen 多選的驗證部分。 驗證工作正常，我只想在多選下拉列表中允許一個選項。 我正在嘗試獲取多選的length ，但它不起作用。 誰能告訴我該怎么做？

請注意，當我單擊“保存”按鈕時，我想顯示一個alert ，例如“請 select 只有一個選項”。

此外，多選有很多選項，但我的情況是，如果下拉菜單包含多個選項，它應該拋出“僅選擇一個選項”錯誤，如上所述。

 $(".chosen-select").chosen(); document.getElementById("plvalidate").addEventListener("click", function(event) { $("#error_sp_msg_pg, #error_sp_msg_soi, #error_sp_msg_cpsea, #error_sp_msg_cpstag, #error_sp_msg_cpvari").remove(); var soilone = document.getElementById("soilval").value; var cpseason = document.getElementById("seasonval").value; var cpstages = document.getElementById("stagval").value; if (soilone == "" || soilone == null) { //alert("Please select atleset one soil type"); $( "<span/>", { "id": "error_sp_msg_soi", "html": "Please select atleset one soil type" }).insertBefore($("#soilval")); event.preventDefault(); } if (cpseason == "" || cpseason == null) { //alert("Please select atleset one season"); $("<span/>", { "id": "error_sp_msg_cpsea", "html": "Please select season" }).insertBefore($("#seasonval")); event.preventDefault(); } else if (cpseason.lenght > 1) { alert('please select only one option'); $("<span/>", { "id": "error_sp_msg_cpsea1", "html": "Please select only one season" }).insertBefore($("#seasonval")); } if (cpstages == "" || cpstages == null) { //alert(""Please select atleset one stage"); $("<span/>", { "id": "error_sp_msg_cpstag", "html": "Please select atleset one stage" }).insertBefore($("#stagval")); event.preventDefault(); } });

 <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script> <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/chosen/1.8.7/chosen.min.css"/> <script src="https://cdnjs.cloudflare.com/ajax/libs/chosen/1.8.7/chosen.jquery.min.js"></script> Test: <select id="soilval" data-placeholder="Select Soil type" class="chosen-select form-control" multiple tabindex="1"> <option>test1</option> <option>test2</option> <option>test3</option> </select> Test2: <select id="seasonval" data-placeholder="Select Season" class="chosen-select form-control" multiple tabindex="1"> <option>Test3</option> <option>Test4</option> <option>Test5</option> </select> Test3 <select id="stagval" data-placeholder="Select Stages" class="chosen-select form-control" multiple tabindex="1"> <option>Test5</option> <option>Test6</option> <option>Test7</option> </select> <button class="btn btn-primary" id="plvalidate">Save</button>

Answer 1

更新了代碼。

$(".chosen-select").chosen();

document.getElementById("plvalidate").addEventListener("click", function(event) {
    $("#error_sp_msg_pg, #error_sp_msg_soi, #error_sp_msg_cpsea, #error_sp_msg_cpstag, #error_sp_msg_cpvari").remove();
    var soilone = $("#soilval").val();
    var cpseason = $("#seasonval").val();
    var cpstages = $("#stagval").val();
    console.log("soilone11", soilone);
    if (soilone == "" || soilone == null) {
        alert("Please select atleset one soil type");
        $(
            "<span/>", {
                "id": "error_sp_msg_soi",
                "html": "Please select atleset one soil type"
            }).insertBefore($("#soilval"));

    }
    $("#error_sp_msg_cpsea1").remove();
    if (cpseason == "" || cpseason == null) {
        //alert("Please select atleset one season");
        $("<span/>", {
            "id": "error_sp_msg_cpsea",
            "html": "Please select season"
        }).insertBefore($("#seasonval"));
        event.preventDefault();
    } else if (cpseason.length > 1) {
        alert('please select only one option');
        $("<span/>", {
            "id": "error_sp_msg_cpsea1",
            "html": "Please select only one season"
        }).insertBefore($("#seasonval"));
    }

    if (cpstages == "" || cpstages == null) {
        //alert(""Please select atleset one stage");
        $("<span/>", {
            "id": "error_sp_msg_cpstag",
            "html": "Please select atleset one stage"
        }).insertBefore($("#stagval"));
        event.preventDefault();
    }
});