nodejs渐入佳境[11]-yargs获取用户输入高级用法

yargs高级用法,用于输出帮助信息,缩写提示等。

app.js:

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//打印字符串
const yargs = require('yargs');
const nodes = require('./nodes.js')

const argv = yargs
.command('add','add a new note',{ //add为命令参数,第二个为说明
title:{ //--titile
describe:'Title of note',
demand:true, //必须要的参数
alias:'t' //缩写 //--t
},
body:{
describe:'Body of note',
demand:true,
alias:'b'
}
})
.command('list','List all notes')
.command('read','Read a note',{
title:{
describe:'Title of note',
demand:true,
alias:'t'
}
})
.command('remove','Remove a note',{
title:{
describe:'Title of note',
demand:true,
alias:'t'
}
})
.help()
.argv;
var command = process.argv[2];

if(command==='add'){
 var note = nodes.addNote(argv.title,argv.body);
if(note){
console.log('add success');
console.log(`title:${note.title}`);
console.log(`body:${note.body}`);
}
}else if(command === 'list'){
var allnotes = nodes.getAll();
allnotes.forEach((note)=>{ console.log(note)});
}else if(command =='read'){
var note = nodes.getNote(argv.title);
if(note){
console.log('find');
console.log(`title:${note.title}`);
console.log(`body:${note.body}`);
}else{
console.log('note not found');
}
}else if(command=='remove'){
var noteRemoved = nodes.removeNote(argv.title);
var message = noteRemoved?'Note was removed':'note not found';
console.log(message);
}else{
console.log('command not find');
}

nodes.js

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console.log('start nodes.js');
const fs = require('fs');
//从文件中获取节点
var fetchNode = ()=>{
try{
var notesString = fs.readFileSync('notes-data.json');
return JSON.parse(notesString);
}catch(e){
return [];
}
}
//保存节点到文件
var saveNote = (notes)=>{

fs.writeFileSync('notes-data.json',JSON.stringify(notes));

}

//增加节点,如果新增返回新增节点。
var addNote = (title,body)=>{
var notes = fetchNode();
var note = {
title,
body
};

//筛选出相同的节点
var duplicateNotes = notes.filter((note)=>note.title===title);
//没有相同的节点
if(duplicateNotes.length ===0){
notes.push(note);
saveNote(notes);
return note;
}
}

var getAll = ()=>{
var notes = fetchNode();
return notes;
};

var getNote = (title)=>{

var notes = fetchNode();
//筛选出相同的节点
var duplicateNotes = notes.filter((note)=>note.title===title);
return duplicateNotes[0];
};

var removeNote = (title)=>{
var notes = fetchNode();
//筛选出不同的节点
var duplicateNotes = notes.filter((note)=>note.title!==title);
saveNote(duplicateNotes);
return notes.length !==duplicateNotes.length;
};

module.exports = {
addNote,
getAll,
getNote,
removeNote
};

测试

打开控制台,在当前目录下输入:

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> node app.js add --help

控制台返回结果:

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app.js add

add a new note

选项:
--version 显示版本号 [布尔]
--help 显示帮助信息 [布尔]
--title, -t Title of note [必需]
--body, -b Body of note [必需]

输入:

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> node app.js  --help

控制台返回结果:

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app.js [命令]

命令:
app.js add add a new note
app.js list List all notes
app.js read Read a note
app.js remove Remove a note

选项:
--version 显示版本号 [布尔]
--help 显示帮助信息 [布尔]