问题:

I am a beginner to express.js and I am trying to understand the difference between res.send and res.write ?

回答1:

res.send

res.send is only in Express js.
Performs many useful tasks for simple non-streaming responses.
Ability to automatically assigns the Content-Length HTTP response header field.
Ability to provides automatic HEAD & HTTP cache freshness support.
Practical explanation
- res.send can only be called once, since it is equivalent to res.write + res.end()
- Example
```
app.get('/user/:id', function (req, res) {
    res.send('OK');
});
```

for more details expressjs.com/en/api.html

res.write

Can be called multiple times to provide successive parts of the body.

Example

response.write('<html>');
response.write('<body>');
response.write('<h1>Hello, World!</h1>');
response.write('</body>');
response.write('</html>');
response.end();

For more details
nodejs.org/docs
nodejs.org/en/docs/guides

回答2:

res.send is equivalent to res.write + res.end So the key difference is res.send can be called only once where as res.write can be called multiple times followed by a res.end.

But apart from that res.send is part of Express. It can automatically detect the length of response header. But there may be be a chance of memory spike with res.send(), in case of large files, our application hangs in between .