Blocking and non-blocking calls of node.js callback functions

First of all, node.js, as a JavaScript running platform, adopts event-driven and asynchronous programming. Through event registration and asynchronous functions, developers can improve resource utilization and server performance can also be improved. Secondly, for front-end people, node.js is the running platform for js. We can write system-level or server-side javascript code and hand it over to node.js for execution, so that our front-end people can also act on the background. In contrast , the browser-side JavaScript code will be subject to various security restrictions when running, and has limited operations on the client system, while node.js is a comprehensive background runtime that provides JavaScript with many functions that other languages ​​can achieve. .

Let’s get back to the topic. First, I will introduce blocking calls to you. Please read below for details.

1. Blocking call (read the file before performing subsequent operations)

var fs = require("fs");
var data = fs.readFileSync('/fs.txt');
console.log(data.toString());
console.log("程序执行结束!");

Output result:

"File content"

"Program execution ends!"

2. Non-blocking calls (reading files and other operations are performed synchronously)

var fs = require("fs"); 
fs.readFile('/fs.txt',function(err,data){
if(err) return console.error(err);
console.log(data.toString());
});
console.log("程序执行结束!");

Output result:

"Program execution ends!"

"File content"

The above content is the node introduced by the editor The entire content of blocking calls and non-blocking calls of .js callback functions, I hope you like it.

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