fs.write json文件以捕获并保存流json文件

Question

I want json stream stored in text file. When running the node server, the json file isn't appended to the json.txt file. What am I missing? Am new to to node, so be gentle..

Here is a code chunk I expect to capture the json content:

var fs = require('fs');
fs.writeFile("json.txt",{encoding:"utf8"}, function(err) {
if(err) {
console.log(err);
} else {
console.log("The file was saved!");
}
});

Answer 1

The issue is you aren't using the correct parameters. When calling fs.writeFile it expects a string for the filename , a buffer or string for the content , an object for the options and a callback function . What it looks like you're doing is sending the options as the second parameter when it expects a buffer or a string. Correction below;

var fs = require('fs');
fs.writeFile("json.txt", JSON.stringify({some: object}), {encoding:"utf8"}, function(err) {
    if(err) {
        console.log(err);
    } else {
        console.log("The file was saved!");
    }
});

You can replace the JSON.stringify part with some plain text if you wanted to, but you specified JSON in your question so I assumed you wanted to store some object in a file

Source (NodeJS documentation)

EDIT: The links to other questions in the comments may be more relevant if you want to add new lines to the end of the file and not completely overwrite the old one. However I made the assumption that fs.writeFile was the intended function. If that wasn't the intention, those other questions will help a lot more

UPDATE:

It seems the issue was the fact that the body wasn't being parsed, so when the POST request was going through, Node didn't have the request body. To alleviate this, during the express configuration, the following code is needed:

var bodyParser = require('body-parser');
app.use(bodyParser.json());

Uses the npm module body-parser . This will convert the JSON body to a JavaScript object, and it is accessible via req.body .