nodejs渐入佳境[9]-保存节点到json文件

原始文件

app.js:

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const yargs = require('yargs');
const nodes = require('./nodes.js')
console.log('Start app.');

console.log(process.argv);

console.log('yargs',yargs.argv);
const argv = yargs.argv;
var command = process.argv[2];

if(command==='add'){
nodes.addNote(argv.title,argv.body);
}else if(command === 'list'){
nodes.getAll();

}else if(command =='read'){
nodes.getNote(argv.title);
}else if(command=='remove'){
nodes.removeNote(argv.title);
}else{
console.log('command not find');
}

nodes.js

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console.log('start nodes.js');
const fs = require('fs');
var addNote = (title,body)=>{
var notes = [];
var note = {
title,
body
};

try{
//读取json文件,读出来是string
var notesString = fs.readFileSync('notes-data.json');
// string转换为json对象
notes = JSON.parse(notesString);
}catch(e){

}
//增加
notes.push(note);
//保存
fs.writeFileSync('notes-data.json',JSON.stringify(notes));
}

var getAll = ()=>{
console.log('Get All notes');
};

var getNote = (title)=>{

console.log('getting note',title);
};

var removeNote = (title)=>{
console.log('Removing note',title);
};

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

打开控制台,在当前目录下输入:

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> node app.js add --title="buy book2" --body="jonson"

将节点添加到notes-data.json文件中.

再次输入:

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> node app.js add --title="buy book2" --body="jonson"

notes-data.json:

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[{"title":"buy book2","body":"jonson"},{"title":"buy book2","body":"jonson"}]

改进 不添加重复的节点

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console.log('start nodes.js');
const fs = require('fs');
var addNote = (title,body)=>{
var notes = [];
var note = {
title,
body
};

try{
var notesString = fs.readFileSync('notes-data.json');
notes = JSON.parse(notesString);
}catch(e){

}

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


}

var getAll = ()=>{
console.log('Get All notes');
};

var getNote = (title)=>{

console.log('getting note',title);
};

var removeNote = (title)=>{
console.log('Removing note',title);
};

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

再次输入不会添加节点:

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> node app.js add --title="buy book2" --body="jonson"