Properties and methods of Array objects in JavaScript

Array object: an array variable is an array object

length property: dynamically obtains the length of the array. For example: var len = arrObj.length

##join()

Function: Convert an array into a string. Returns a string.
Syntax: arrObj.join (connection number)
Description: Connect an array into one character using the specified "connection number" string.

<!DOCTYPE HTML>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
        <title>php.cn</title>
        <script>
           //将以下字符串转成数组， 然后再转成字符串
           var str = "北京,上海,深圳,南京,合肥";  
           //转成数组
           var arr=str.split(",");
           //再转换成字符串
           str = arr.join(",") ;
           document.write("类型是："+typeof(str)+",字符串为："+str);
        </script>
    </head>
    <body>
    </body>
</html>

##reverse()

<!DOCTYPE HTML>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
        <title>php.cn</title>
        <script>
          var arr=[1,2,3,4,5,6,7,8];
          arr.reverse();
          document.write(arr);
        </script>
    </head>
    <body>
    </body>
</html>

Deletion and addition of array elements

delete operation symbol, only the value of the array element can be deleted, but the space occupied is still there, and the total length has not changed (arr.length).

#Previous array elements can only be added backward, not forward.

<!DOCTYPE HTML>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
        <title>php.cn</title>
        <script>
            //使用delete删除元素，查看长度是否改变
            var arr=[1,2,3,4,5,6,7,8];
            document.write("数组的长度为"+arr.length+",值为"+arr+"<br/>");
            delete arr[0];
            delete arr[1];
            delete arr[2];
            document.write("数组的长度为"+arr.length+",值为"+arr+"<br/>");
        </script>
    </head>
    <body>
    </body>
</html>

shift(): Delete the first element in the array, return the deleted value, and reduce the length by 1.

pop(): Delete the last element in the array, return the deleted value, and reduce the length by 1.

<!DOCTYPE HTML>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
        <title>php.cn</title>
        <script>
            //使用delete删除元素，查看长度是否改变
            var arr=[1,2,3,4,5,6,7,8];
            document.write("数组的长度为"+arr.length+",值为"+arr+"<br/>");
            arr.shift();
            document.write("数组的长度为"+arr.length+",值为"+arr+"<br/>");
            arr.pop();
            document.write("数组的长度为"+arr.length+",值为"+arr+"<br/>");
        </script>
    </head>
    <body>
    </body>
</html>

unshift(): Add one or more array elements to the front of the array, and the length needs to be changed. arrObj.unshift("a", "b", "c")

push(): Add one or more array elements to the end of the array, length To change. arrObj.push(“a” , “b” , “c”)

<!DOCTYPE HTML>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
        <title>php.cn</title>
        <script>
            //使用delete删除元素，查看长度是否改变
            var arr=[1,2,3,4,5,6,7,8];
            document.write("数组的长度为"+arr.length+",值为"+arr+"<br/>");
            arr.unshift(0);
            document.write("数组的长度为"+arr.length+",值为"+arr+"<br/>");
            arr.push(9);
            document.write("数组的长度为"+arr.length+",值为"+arr+"<br/>");
        </script>
    </head>
    <body>
    </body>
</html>

Continuing Learning

new file

<!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>php.cn</title> <script> //将以下字符串转成数组，然后再转成字符串 var str = "北京,上海,深圳,南京,合肥"; //转成数组 var arr=str.split(","); //再转换成字符串 str = arr.join(",") ; document.write("类型是："+typeof(str)+",字符串为："+str); </script> </head> <body> </body> </html>

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Properties and methods of Array objects in JavaScript

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