How Can I Set Response Header on Express. Js Assets

This is so annoying.

Okay if anyone is still having issues or just doesn't want to add another library. All you have to do is place this middle ware line of code before your routes.

Cors Example

app.use((req, res, next) => {
    res.append('Access-Control-Allow-Origin', ['*']);
    res.append('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
    res.append('Access-Control-Allow-Headers', 'Content-Type');
    next();
});

// Express routes
app.get('/api/examples', (req, res)=> {...});

Short Answer:

• res.setHeaders - calls the native Node.js method

• res.set - sets headers

• res.headers - an alias to res.set

You can do this by using cors. cors will handle your CORS response

var cors = require('cors')

app.use(cors());

@klode's answer is right.

However, you are supposed to set another response header to make your header accessible to others.

Example:

First, you add 'page-size' in response header

response.set('page-size', 20);

Then, all you need to do is expose your header

response.set('Access-Control-Expose-Headers', 'page-size')

There is at least one middleware on npm for handling CORS in Express: cors.

You can also add a middleware to add CORS headers, something like this would work:

/**
 * Adds CORS headers to the response
 *
 * {@link 
 * {@link 
 * @param {object} request the Request object
 * @param {object} response the Response object
 * @param {function} next function to continue execution
 * @returns {void}
 * @example
 * <code>
 * const express = require('express');
 * const corsHeaders = require('./middleware/cors-headers');
 *
 * const app = express();
 * app.use(corsHeaders);
 * </code>
 */
module.exports = (request, response, next) => {
    // 
    response.set({
        'Access-Control-Allow-Origin': '*',
        'Access-Control-Allow-Methods': 'DELETE,GET,PATCH,POST,PUT',
        'Access-Control-Allow-Headers': 'Content-Type,Authorization'
    });

    // intercept OPTIONS method
    if(request.method === 'OPTIONS') {
        response.send(200);
    } else {
        next();
    }
};

First add 'field' in response header

response.set('field', 'value');

Then you need to do is expose your header

response.set('Access-Control-Expose-Headers', 'field')