Beginner LevelExpress JS
How do you set custom response HTTP headers in Express using res.set() and res.append()?
❓ Interview Prompt: Explain setting response headers via res.set(), object map syntax, and appending header values with res.append().
Express provides methods for modifying outgoing HTTP response headers before sending content:
1. 'res.set(field, value)':
Sets a single header or an object map of headers: 'res.set("X-API-Version", "2.0")'. Overwrites any previously set value.
2. 'res.append(field, value)':
Appends additional values to an existing header array without overwriting prior values (ideal for multiple 'Set-Cookie' headers).
Code Implementation Example
javascript
import express from 'express';
const app = express();
app.get('/api/custom-headers', (req, res) => {
// Set multiple headers using object syntax
res.set({
'X-API-Version': 'v2.4',
'Cache-Control': 'no-store'
});
res.append('Warning', '199 Miscellaneous warning');
res.json({ status: 'Headers set successfully' });
});💡Setting custom response headers via res.set and res.append.
🎯 Interview Key Takeaway
Use res.set() to set or overwrite response headers, and res.append() to append values without overwriting.
#res.set#res.append#Headers#Beginner
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