javascript 将对象添加到 json 文件 - Node.js
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Add object to json file - Node.js
提问by sanjaypoyzer
I'm trying to add an object to a very large JSON file in Node.js (but only if the id doesn't match an existing object). What I have so far:
我正在尝试将一个对象添加到 Node.js 中的一个非常大的 JSON 文件中（但前提是 id 与现有对象不匹配）。到目前为止我所拥有的：
example JSON file:
JSON 文件示例：
[
{
id:123,
text: "some text"
},
{
id:223,
text: "some other text"
}
]
app.js
应用程序.js
var fs = require('fs');
var jf = require('jsonfile')
var util = require('util')
var file = 'example.json'
// Example new object
var newThing = {
id: 324,
text: 'more text'
}
// Read the file
jf.readFile(file, function(err, obj) {
// Loop through all the objects in the array
for (i=0;i < obj.length; i++) {
// Check each id against the newThing
if (obj[i].id !== newThing.id) {
found = false;
console.log('thing ' + obj[i].id + ' is different. keep going.');
}else if (obj[i].id == newThing.id){
found = true;
console.log('found it. stopping.');
break;
}
}
// if we can't find it, append it to the file
if(!found){
console.log('could not find it so adding it...');
fs.appendFile(file, ', ' + JSON.stringify(newTweet) + ']', function (err) {
if (err) throw err;
console.log('done!');
});
}
})
This is soclose to what I want. The only problem is the trailing ]character at the end of the JSON file. Is there a way to delete it using the file system API or something? Or is there a much easier way to do exactly what I want?
这与我想要的非常接近。唯一的问题是]JSON 文件末尾的尾随字符。有没有办法使用文件系统 API 或其他方法删除它？或者有没有更简单的方法来做我想做的事？
回答by Brad
The proper way to handle this is to parse the JSON file, modify the object, and output it again.
处理这个问题的正确方法是解析 JSON 文件，修改对象，然后再次输出。
var obj = require('file.json');
obj.newThing = 'thing!';
fs.writeFile('file.json', JSON.stringify(obj), function (err) {
console.log(err);
});
回答by ChrisRich
For my project I ended up using this code.
对于我的项目，我最终使用了此代码。
function appendJsonToFile(file, entry, key, callback){
if(!_.isObject(entry)){
return callback('Type object expected for param entry', null);
}
fs.readFile(file, 'utf8', function(err, data){
if(err){
return callback(err, null);
}
var json;
try{
json = JSON.parse(data);
} catch(e){
return callback(e, null);
}
if(!_.isArray(json[key])){
return callback('Key "' + key + '" does not point to an array', null);
}
json[key].push(entry);
fs.writeFile(file, JSON.stringify(json), function (err) {
if(err){
return callback(err, null);
}
callback(null, file);
});
});
}
