Express JS中的正文解析器

Question

I have been messing around with express js for a while now and I have come across something called body parser. According to my research body parser allows us to POST content form our HTTP request.

My question that, is it absolutely necessary to use body parser when using express.js?

If it is not necessary then what are the advantages of using it and if body parser is not used then what needs to be done to make sure that the content is POSTED?

Thank you in advance.

Answer 1

Let's try to keep this least technical.

Let's say you are sending a html form data to node-js server ie you made a request to the server. The server file would receive your request under a request object. Now by logic, if you console log this request object in your server file you should see your form data some where in it, which could be extracted then, but whoa ! you actually don't !

So, where is our data ? How will we extract it if its not only present in my request.

Simple explanation to this is http sends your form data in bits and pieces which are intended to get assembled as they reach their destination. So how would you extract your data. Use something called “body-parser” which would do this for you.

body-parser parses your request and converts it into a format from which you can easily extract relevant information that you may need. First of all require the following in your app.js file.

var bodyParser = require('body-parser')

and add the following line to make it work

app.use(bodyParser.urlencoded({extended: true}));

Answer 2

You can make use of the events on('data') and on('end') to extract the payload. Whenever a POST request is sent, data arrives as a stream of bits. When the stream comes in the on('data') event is fired, and you can start collecting the stream into a buffer. When the stream ends (all the data has been received) the on('end') event is fired, that is when you can start using the data that you just collected.

Yopu need to include stringDecoder (stringDecoder is a module that comes built into node)

const string_decoder= require('string_decoder').StringDecoder;

You need to have this piece of code running as middleware.

var buffer= "";
request.on('data',  function(data_stream)
{
    //start collecting the data stream into a buffer
    buffer= buffer + utf8_decoder.write(data_stream);
});

request.on('end', function()
{
    buffer= buffer + utf8_decoder.end();
    //add the buffer to the request object so it can be accessed elsewhere
    request.payload= buffer;
});

This is probably the best way if you decide not to use any external libraries.