const fs = require('fs');
const path = require('path');
fs.readFile(path.join(__dirname, 'data/a.txt'), (err, data)=>{
console.log(data.toString());
fs.readFile(path.join(__dirname, 'data/b.txt'), (err, data)=>{
console.log(data.toString());
fs.readFile(path.join(__dirname, 'data/c.txt'), (err, data)=>{
console.log(data.toString());
});
});
});
const fs = require('fs');
const path = require('path');
// 1. 创建一个promise （一经创建， 立马执行）链式编程
new Promise((resolve, reject)=>{
fs.readFile(path.join(__dirname, 'data/a.txt'), (err, data)=>{
if(err){
reject(err);
}
resolve(data);
});
}).then((data)=>{
console.log(data.toString());
return new Promise((resolve, reject)=>{
fs.readFile(path.join(__dirname, 'data/b.txt'), (err, data)=>{
if(err){
reject(err);
}
resolve(data);
});
});
}).then((data)=>{
console.log(data.toString());
return new Promise((resolve, reject)=>{
fs.readFile(path.join(__dirname, 'data/c.txt'), (err, data)=>{
if(err){
reject(err);
}
resolve(data);
});
});
}).then((data)=>{
console.log(data.toString());
}).catch((err)=>{
console.log(err);
});
1 const fs = require('fs');
2 const path = require('path');
3
4 let readFile = (...args) => {
5 return new Promise((resolve, reject) => {
6 fs.readFile(...args, (err, data) => {
7 if (err) {
8 reject(err);
9 }
10 resolve(data);
11 });
12 });
13 };
14
15 readFile(path.join(__dirname, 'data/c.txt'), 'utf-8')
16 .then((data) => {
17 console.log(data.toString());
18 return readFile(path.join(__dirname, 'data/a.txt'), 'utf-8');
19 }).then((data) => {
20 console.log(data.toString());
21 return readFile(path.join(__dirname, 'data/b.txt'), 'utf-8');
22 }).then((data) => {
23 console.log(data.toString());
24 }).catch((err)=>{
25 console.log(err);
26 });
1 const fs = require('fs');
2 const path = require('path');
3
4 let readFile = (...args) => {
5 return new Promise((resolve, reject) => {
6 fs.readFile(...args, (err, data) => {
7 if (err) {
8 reject(err);
9 }
10 resolve(data);
11 });
12 });
13 };
14
15 Promise.all([
16 readFile(path.join(__dirname, 'data/aa.txt'), 'utf-8'),
17 readFile(path.join(__dirname, 'data/b.txt'), 'utf-8'),
18 readFile(path.join(__dirname, 'data/c.txt'), 'utf-8')
19 ]).then(([data1, data2, data3])=>{
20 console.log({data1, data2, data3});
21 }).catch((err)=>{
22 console.log(err);
23 });