正文解析器的req.body返回未定义

Question

I keep getting undefined for req.body . Why?

var express = require('express'),
    app = require('express')(),
    bodyParser = require('body-parser');

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

app.post('/', function (req, res) {
    console.log(req.body.username)
});

EDIT : The above snippet is a simplified version, I thought I encompassed everything involved, but it runs fine. Here's the entire code: https://jsfiddle.net/dx9kswdy/

Answer 1

print out req only, if it is still undefined than it is not assigned a value when passed into the function. if it returns a JSON file, parse it to an object!

app.post('/', function (req, res) {
    console.log(JSON.parse(req).body.username);
});

Answer 2

When I started up your example, it logged the username from the body for me

curl -X POST -d '{"username": "doug"}' -H "content-type: application/json" localhost:3000

dougwade npm-experiments/express-undef » node index.js doug

What symptom are you getting? Is it an actual error, or are you just logging "undefined"? If you're just logging undefined, the problem is that the key username isn't found on your (correctly parsed) body. If you're getting an error, please post the full trace.

Edit: pulled the fiddle and ran it. Had to remove some relative imports, but your use of body-parser is just fine:

dougwade npm-experiments/express-undef » node index.js doug ReferenceError: user is not defined at /Users/doug.wade/npm-experiments/express-undef/index.js:23:9 at Layer.handle [as handle_request] (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/layer.js:95:5) at next (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/route.js:131:13) at Route.dispatch (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/route.js:112:3) at Layer.handle [as handle_request] (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/layer.js:95:5) at /Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/index.js:277:22 at Function.process_params (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/index.js:330:12) at next (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/index.js:271:10) at /Users/doug.wade/npm-experiments/express-undef/node_modules/body-parser/lib/read.js:129:5 at invokeCallback (/Users/doug.wade/npm-experiments/express-undef/node_modules/raw-body/index.js:262:16)

from the request:

dougwade npm-experiments/express-undef » curl -X POST -d '{"username": "doug"}' -H "content-type: application/json" localhost:3000 ReferenceError: user is not defined<br> &nbsp; &nbsp;at /Users/doug.wade/npm-experiments/express-undef/index.js:23:9<br> &nbsp; &nbsp;at Layer.handle [as handle_request] (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/layer.js:95:5)<br> &nbsp; &nbsp;at next (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/route.js:131:13)<br> &nbsp; &nbsp;at Route.dispatch (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/route.js:112:3)<br> &nbsp; &nbsp;at Layer.handle [as handle_request] (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/layer.js:95:5)<br> &nbsp; &nbsp;at /Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/index.js:277:22<br> &nbsp; &nbsp;at Function.process_params (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/index.js:330:12)<br> &nbsp; &nbsp;at next (/Users/doug.wade/npm-experiments/express-undef/node_modules/express/lib/router/index.js:271:10)<br> &nbsp; &nbsp;at /Users/doug.wade/npm-experiments/express-undef/node_modules/body-parser/lib/read.js:129:5<br> &nbsp; &nbsp;at invokeCallback (/Users/doug.wade/npm-experiments/express-undef/node_modules/raw-body/index.js:262:16)

Answer 3

I've run into this a couple times, and here's what it usually ends up being:

When you're making your request with curl/the browser, make sure you set the Content-Type header to application/json . That's what triggers Express / the Express body parser to parse the string as JSON.