Question

我想将值推送到数组的末尾，但由于某种原因它不起作用。当我单击按钮时，它应该将值添加到数组的末尾。然后，如果我再次点击它，它应该告诉我它仍然存在，但它只是保持pushin到阵列。如何将值保留在数组中。

    <html>
    <head>
        <script>
            function myFunction() {
                var asdf = ["a","b","c","e"];
                if (asdf.indexOf("d")==-1) {
                    asdf.push("d");
                    alert(asdf.indexOf("d")+"It has been pushed to the end.");
                } else {
                    alert(asdf.indexOf("d")+"It is still there.");
                }
            }
        </script>
    </head>
    <body>
        <input type="button" onclick="myFunction()" value="Show alert">
    </body>
    </html>

Answer 1

这是因为你在函数内部声明了asdf。因此，当函数完成时，asdf变量将被删除，然后在您下次单击按钮时重新创建。相反，你需要使它成为全球性的：

<html>
<head>
    <script>
        window.asdf = ["a","b","c","e"];
        function myFunction() {
            if (window.asdf.indexOf("d")==-1) {
                window.asdf.push("d");
                alert(window.asdf.indexOf("d")+"It has been pushed to the end.");
            } else {
                alert(window.asdf.indexOf("d")+"It is still there.");
            }
        }
    </script>
</head>
<body>
    <input type="button" onclick="myFunction()" value="Show alert">
</body>
</html>

Answer 2

每次调用myFunction时，都会从头开始构建数组asdf。

这样的事情会起作用：

var myFunction = (function () {
    // This line is only run once.
    var asdf = ["a", "b", "c", "e"];

    // This is run with every call to myFunction, and will reuse the array
    return function () {
        if (asdf.indexOf("d") == -1) {
            asdf.push("d");
            alert(asdf.indexOf("d") + "It has been pushed to the end.");
        } else {
            alert(asdf.indexOf("d") + "It is still there.");
        }

    };

}());

推送到数组的值不会停留

2 个答案: