How to introduce remote js in javascript

Javascript is a very popular scripting language, mainly used to achieve dynamic effects on web pages. In order to facilitate developers to quickly build web pages, many third-party libraries and frameworks are published to remote servers in the form of js files. Therefore, we need to use these third-party libraries and frameworks in our web pages by introducing remote js files. This article will introduce how Javascript introduces remote js.

1. The script tag introduces remote js

The most common way is to use the script tag to introduce remote js files. We only need to add the following code to the web page:

where , the src attribute specifies the address of the remote js file. We only need to replace the address with the corresponding target file to import.

2. Dynamicly create script elements to introduce remote js

In some business scenarios, we need to dynamically introduce remote js. In this case, we can use Javascript to dynamically create script elements. The code example is as follows:

var script = document.createElement("script");
script.type = "text/javascript";
script.src = "http://remote-server .com/script.js";
document.head.appendChild(script);

We first create a script element using the createElment method, then set its type and src attributes, and finally add the script element to At the head of the document, the introduction is completed.

3. Ajax request to obtain remote js code

In addition to the above two methods, we can also use Ajax request to obtain remote js code. In this way, we can freely handle the js code, such as dynamic execution through the eval function after the code returns. The code example is as follows:

var xhr = new XMLHttpRequest();
xhr.open('GET', 'http://remote-server.com/script.js', true);
xhr.onreadystatechange = function() {
if (xhr.readyState === 4 && xhr.status === 200) {

eval(xhr.responseText);

}
};
xhr.send ();

We use the XMLHttpRequest object to send a GET request, return the remote js code as a response, and then use the eval function to parse and execute the code.

It should be noted that when introducing remote js, some best practices should be followed, such as: only introduce necessary code to reduce unnecessary requests; when introducing third-party libraries, CDN should be used to improve Access speed and cache efficiency, etc.

Conclusion

This article introduces several ways of how Javascript introduces remote js, including using script tags, dynamically creating script elements and Ajax requests to obtain js code. Through these methods, we can easily introduce remote Javascript files, speed up development efficiency, and achieve better effects on web pages. Of course, when introducing js, we also need to pay attention to some best practices to ensure the correctness and security of the code.

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