(1) Highlights of javascript in Silicon Valley (2) [Array] [Function]

1. Array definition method

The length in the document is wrong, not 0, but 2

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">

        var arr = [true,1]; // 定义一个空数组
         alert( arr.length ); // 2

        arr[0] = 12;
        // alert( arr[0] );//12
         alert( arr.length ); // 2

        // javaScript语言中的数组,只要我们通过数组下标赋值,那么最大的下标值,就会自动的给数组做扩容操作。
        arr[2] = "abc";
        alert(arr.length); //3

        // alert(arr[1]);// undefined
        // 数组的遍历
        for (var i = 0; i < arr.length; i++){
            alert(arr[i]);
        }

    </script>
</head>
<body>
</body>
</html>

2. Two definitions of functions

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
        // 定义一个无参函数
        function fun(){
            alert("无参函数fun()被调用了");
        }
        // 函数调用===才会执行
        // fun();

        function fun2(a ,b) {
            alert("有参函数fun2()被调用了 a=>" + a + ",b=>"+b);
        }

        // fun2(12,"abc");

        // 定义带有返回值的函数
        function sum(num1,num2) {
            var result = num1 + num2;
            return result;
        }

        alert( sum(100,50) );

    </script>
</head>
<body>

</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
        var fun = function () {
            alert("无参函数");
        }
        // fun();

        var fun2 = function (a,b) {
            alert("有参函数a=" + a + ",b=" + b);
        }
        // fun2(1,2);

        var fun3 = function (num1,num2) {
            return num1 + num2;
        }

        alert( fun3(100,200) );
    </script>

</head>
<body>

</body>
</html>

 

Note: Functions are allowed to be overloaded in Java . But the overloading of the function in JS will directly overwrite the last definition
 
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">


        function fun(a,b) {
            alert("有参函数fun(a,b)");
        }

        function fun() {
            alert("无参函数fun()");
        }

        fun(1,"ad");

    </script>
</head>
<body>

</body>
</html>

 

 

 

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Origin blog.csdn.net/qq_41048982/article/details/108970773