引用类型的值传递与原始类型的值传递

1.原始类型的值传递

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <script type="text/javascript">
        var a = 10;
        var b = a;
        a = 20;
        console.log(a,b);
    </script>
</body>
</html> 

运行结果:20 10

引用类型值传递

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
</head>
<body>
    <script type="text/javascript">
/*      var a = 10;
        var b = a;
        a = 20;
        console.log(a,b);*/
        var arr = [1,2,3,4,56,7,78];
        var arr1 =arr;
        arr[0] = "hello";
        console.log(arr,arr1);
    </script>
</body>
</html> 

运行结果:(7) ["hello", 2, 3, 4, 56, 7, 78] (7) ["hello", 2, 3, 4, 56, 7, 78]

在引用类型中变量保存的是一个地址，传值时将这个地址传递出去，当一处修改值时就会修改所有引用此地址变量的值