node中有json2csv模块，但是当json数据的key未事先指定，并且有嵌套结构的时候，嵌套在内层的数据无法被识别并转换。
参考一个在线的json to csv转换工具Convert JSON to CSV，及其源码parse_object 和 csvkit
先对json数据进行递归遍历，将其拍平，然后再利用json2csv模块。
代码如下：
var fs = require('fs');
var filename = 'data.txt';
function allItems(filename) {
console.log("read file", filename)
var contents = fs.readFileSync(filename).toString().split("\n")
var arr = []
contents.forEach(s => {
try {
arr.push(JSON.parse(s))
} catch (e) {
console.log("parse error", e)
console.log("parse error", s)
}
})
return arr
}
function parseObject(obj, path) {
if (path == undefined)
path = "";
var type = obj.constructor;
var scalar = (type == Number || type == String || type == Boolean || type == null);
if (type == Array || type == Object) {
var d = {};
for (var i in obj) {
var newD = parseObject(obj[i], path + i + ".");
Object.assign(d, newD);
}
return d;
}
else if (scalar) {
var d = {};
var endPath = path.substr(0, path.length-1);
d[endPath] = obj;
return d;
}
else return {};
}
function csv() {
var arr = allItems(filename);
var arrNew = [];
var json2csv = require('json2csv');
for(var i in arr) {
arrNew.push(parseObject(arr[i]));
}
try {
var result = json2csv({ data: arrNew });
fs.writeFile(filename+'.csv', result);
} catch (err) {
// Errors are thrown for bad options, or if the data is empty and no fields are provided.
// Be sure to provide fields if it is possible that your data array will be empty.
console.error("convert", err, err.stack);
}
}
csv()
