Question

我创建了一个带有按钮的HTML页面，显示一条消息：＆＃34;这是一条消息＆＃34;。一切都很好，但是当我按下按钮时，不会收到消息。我检查过任何错误，但我找不到任何错误。我做错了什么？

<!DOCTYPE html>

<html>
<head>
    <title>Testing JavaScript</title>
    <link rel="stylesheet" type="css" href="Button.css">
</head>

<body>
    <h1>Javascript</h1>
        <p>I am testing JS on this page.<br/>
        This is a button.</p>

    <script>
        var message = "This is a message";
        function popUp()
        {
            alert(message);
        }
    </script>
    <button type="button" onclick="press()">Press me!</button>
</body>
</html>

Answer 1

您应该致电onclick="popUp()"

Answer 2

而不是struct Pond : Storable { static let hash = "Pond" let pk: Int let depth: Int } struct Frog { let pk: Int let name: String let pondPk: Int? weak var store: Store? // reference to central Store() var pond: Pond? { guard let pondPk = pondPk else { return nil } return store?.fetch(Pond.self, withPk: pondPk) as? Pond } }：

func printPondDepth(frog: Frog) {
    if let _ = frog.pondPk {
        print(frog.pond?.depth ?? "No pond with id \(frog.pondPk ?? 0) in frog \(frog.name):s associated store")
    }
    else {
        print("No pond id associated with frog \(frog.name)")
    }
}

/* Central store */
let store = Store()

/* Some frogs read prior to any Ponds being added to the store */
let frog = Frog(pk: 1, name: "Kermit", pondPk: 1, store: store)
let anotherFrog = Frog(pk: 2, name: "Mitker", pondPk: 3, store: store)

/* Adding ponds to the store */
store.add(Pond(pk: 1, depth: 4))
store.add(Pond(pk: 4, depth: 25))

/* another frog and some attempts to get the depth of the 
   pond in which a frog possibly resides */
let thirdFrog = Frog(pk: 3, name: "Kerker", pondPk: nil, store: store)

printPondDepth(frog)        /* 4 */
printPondDepth(anotherFrog) /* No pond with id 3 in frog Mitker:s associated store */
printPondDepth(thirdFrog)   /* No pond id associated with frog Kerker */

Answer 3

您没有声明名为“press（）”的函数，更改代码

<!DOCTYPE html>

<html>
<head>
    <title>Testing JavaScript</title>
    <link rel="stylesheet" type="css" href="Button.css">
</head>

<body>
    <h1>Javascript</h1>
        <p>I am testing JS on this page.<br/>
        This is a button.</p>

    <script>
        var message = "This is a message";
        function popUp()
        {
            alert(message);
        }
    </script>
    <button type="button" onclick="popUp()">Press me!</button>
</body>
</html>

HTML / Javascript按钮不会返回警报

3 个答案: