Nodejs (II) read files synchronously and asynchronously

var fs = require("fs");
var data = fs.readFileSync('test.txt');
console.log(data.toString());
console.log("Program Ended 001"); 

fs.readFile('test.txt', function (err, data) {
    if (err) return console.error(err);
    console.log(data.toString());
});
console.log("Program Ended 002"); 

introduce fs modular , Synchronous read function readFileSync, Asynchronous read function readFile. 

In general NodeJS Every one of API It's all asynchronous , As a single thread , It USES An asynchronous function Transfer to Maintenance concurrency .Node Using observer mode .Node The thread maintains an event loop , Whenever any task is completed, you get the result , It triggers the notification event listener function to execute the corresponding event .