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How to use built-in functions and custom functions in JS

php中世界最好的语言Original: 2017-11-28 13:51:252488browse

Today I will talk to you about JS’s built-in functions and custom functions, how to use JS’s built-in functions and custom functions, and what are the uses of JS’s built-in functions and custom functions Note, here are two cases for you.

There are two ways to execute JS code, one is to refresh the interface, and the other is to write it in the click event. When clicking, execute the JS code

function Parameter : The formal parameters (formal parameters) placed in the defined function are not limited in number. The value passed by the calling function is the actual parameter, and the formal parameter is the access to the corresponding

variable. Regarding value acquisition and assignment

The variables written between the script tags are called global variables (top-level variables). The scope of the variable is the top-level scope

When the variable When defined in a function, the variable can only be accessed within the function

JS follows the upward search rule when searching for variables (first search for variables within its own scope)

As long asDefine a function will generate a scope

The scope search rule is the scope chain

First search for variables in its own scope, and upward query

will not Execute downward search

Now a is a global variable

1. JavaScript built-in function

escape function: URL-encode the incoming string.

unescape function: Convert the incoming url encoding to the original string.

It should be noted that the URL encoding rules are:

(1) English alphanumeric: not encoded.

(2) Blank punctuation marks: converted to %xx string, for example, blank characters are converted to %20.

(3) Chinese characters: converted to %xxxx string, which is hexadecimal system.

<!doctype html>  
<html>  
 <head>  
    <meta charset="gb2312">  
    <title>实验</title>  
    </script>   
 </head>  
   
 <body>  
    <script language="javascript">  
           
        var str = "javascript学习基础";  
   
        var strEscape = escape(str);              
        var strOriginal = unescape(strEscape);    
   
        console.log(strEscape);  // javascript%u5B66%u4E60%u57FA%u7840  
        console.log(strOriginal);// javascript学习基础  
    </script>  
 </body>  
</html>

Custom function

can take no parameters, take parameters, and include return values.

<!doctype html>  
<html>  
 <head>  
    <meta charset="gb2312">  
    <title>实验</title>  
    <script language="javascript">  
           
        //带2个参数，返回值  
        function f2(a,b)  
        {  
            return a + parseInt(b);  
        }  
           
        //不带参数，无返回值  
        function f1()  
        {  
            var r;  
            r = f2(2,&#39;8xx&#39;);  
            document.write(r);    
        }  
    </script>  
 </head>  
   
 <body>  
    <script language="javascript">  
        f1(); //输出10  
    </script>  
 </body>  
</html>

I believe you have mastered the methods after reading these cases. For more exciting information, please pay attention to other related articles on the php Chinese website!

How to use built-in functions and custom functions in JS

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