connect-injector

0.4.4 verified Sat Apr 25 auth: no javascript maintenance

A middleware to inject content into any HTTP response, compatible with Connect and Express. Version 0.4.4 is the latest stable release (last updated in 2014). It allows conditional injection based on request/response headers and can modify response buffers on the fly. Key differentiator: intercept and transform responses before they are sent, unlike typical request-based middleware. Works with http-proxy for proxied content rewriting. Simple boolean condition function and a content converter function. No longer actively maintained; consider alternatives like express-transform or custom middleware.

Common errors

error TypeError: Cannot read property 'indexOf' of undefined ↓

cause The condition function tries to call indexOf on undefined content-type header.

fix

Check if res.getHeader('content-type') is defined before calling indexOf: return res.getHeader('content-type') && res.getHeader('content-type').indexOf('text/html') !== -1;

error Error: connect-injector must be used before any middleware that writes to the response ↓

cause The injector was placed after a middleware that already started writing or ended the response.

fix

Move injector middleware before any response-writing middleware.

Warnings

deprecated Package has not been updated since 2014. No longer maintained. ↓

fix Consider using alternatives like express-transform or write a custom middleware.

gotcha The injector must be placed before any middleware that writes the response, otherwise it won't intercept. ↓

fix Place injector middleware early in the stack, before any middleware that calls res.end() or res.write().

gotcha If the response has no content-type header, condition function may crash when accessing res.getHeader('content-type'). ↓

fix Always check if the header exists before using its value: res.getHeader('content-type') && res.getHeader('content-type').indexOf(...).

Install

npm install connect-injector

yarn add connect-injector

pnpm add connect-injector

Imports

default
wrong
```
import injector from 'connect-injector'
```
correct
```
var injector = require('connect-injector');
```
Package is CommonJS only; does not support ESM natively. Use require().

injector function

wrong

var inject = injector({ when: function(req, res) { return true; }, convert: function(data, req, res, callback) {} });

correct

var inject = injector(function(req, res) { return true; }, function(data, req, res, callback) { callback(null, data); });

The module exports a single function that takes two arguments: a condition function and a converter function. Do not pass an options object.

None (require only)
```
var injector = require('connect-injector');
```
No named exports. Use default require.

Quickstart

Demonstrates a basic connect-injector middleware that appends a paragraph to all HTML responses.

var connect = require('connect');
var injector = require('connect-injector');

var app = connect();

// Inject 'injected' into all text/html responses
var inject = injector(function(req, res) {
  return res.getHeader('content-type') && res.getHeader('content-type').indexOf('text/html') === 0;
}, function(data, req, res, callback) {
  var injectedContent = data.toString() + '<p>injected</p>';
  callback(null, injectedContent);
});

app.use(inject);
app.use(function(req, res) {
  res.setHeader('content-type', 'text/html');
  res.end('<html><body>Hello</body></html>');
});

app.listen(3000);
console.log('Server running on port 3000');