javascript - knockoutJS 中的验证码不起作用

Question

这是验证两个输入字段 firstname 和 lastname 的示例，both 这两个字段都是必需的

查看

<p data-bind="css: { error: firstName.hasError }">
    FirstName :<input data-bind='value: firstName, valueUpdate: "afterkeydown"' required />
    <span data-bind='visible: firstName.hasError, text: firstName.validationMessage' > </span>
</p>
<p data-bind="css: { error: lastName.hasError }">
    LastName : <input data-bind='value: lastName, valueUpdate: "afterkeydown"' required/>
    <span data-bind='visible: lastName.hasError, text: lastName.validationMessage'> </span>
</p>

View 模型

ko.extenders.required = function(target, overrideMessage) {
    //add some sub-observables to our observable
    target.hasError = ko.observable();
    target.validationMessage = ko.observable();

    //define a function to do validation
    function validate(newValue) {
       target.hasError(newValue ? false : true);
       target.validationMessage(newValue ? "" : overrideMessage || "This field is required");
    }

    //initial validation
    validate(target());

    //validate whenever the value changes
    target.subscribe(validate);

    //return the original observable
    return target;
};


function AppViewModel(first, last) {
    this.firstName = ko.observable(first).extend({ required: "Please enter a first name" });
    this.lastName = ko.observable(last).extend({ required: "" });
}

ko.applyBindings(new AppViewModel("Bob","Smith"));

CSS

.error
{
  background-color: #f5f5f5; 
}

我尝试在 JSFiddle 中运行这段代码.但它不起作用，即使初始值也未显示在输入字段 FirstName 和 LastName 中。我无法找出错误。

Answer 1

您包括了 knockout 文库吗？它似乎对我有用。 https://jsfiddle.net/co2y5x60/

https://cdnjs.cloudflare.com/ajax/libs/knockout/3.4.0/knockout-min.js