JavaScript fetch request: proxy IP to resolve CORS limitations

First, why your fetch request is always blocked?CORS in the end this thing how the matter

When you write front-end code, you've definitely encountered this crap: requesting another website's interface with fetch, and the browser just throws you a red face - a CORS error. It's like a janitorial gatekeeper who insists on a "same-origin policy" that prevents cross-domain requests. But sometimes we just need to tune other people's interfaces, such as third-party data matching and so on, so what should we do?

Traditional solutions have to makeServer-side cooperation in setting response headersBut the reality is very hard: many of the old interfaces simply won't change for you! This is where proxy IPs come into play. Its principle is like finding a middleman to help you pass the message, so that the browser thinks that the request is for its own server, perfectly bypassing the CORS restrictions.

Second, hand to teach you to use proxy IP get fetch request

Here's an example of ipipgo's proxy service (Highlighted Recommendation! Stability Carrier), demonstrating specific operations:

// The original intercepted request
fetch('https://其他域名/api/data')
  .then(response => response.json())
  .catch(err => console.error('Done:', err))

// The request after changing to a proxy
const proxyUrl = 'https://api.ipipgo.com/proxy?target='
const targetUrl = encodeURIComponent('https://其他域名/api/data')

fetch(proxyUrl + targetUrl, {
  headers: {
    'Authorization': 'Bearer your ipipgo key'
  }
})
.then(/ normal processing logic /)

Knockout! Note these two key points:

1. Transcode the destination address with encodeURIComponent to prevent special characters from messing with it
2. Put the authentication information provided by ipipgo in the request header, so that the proxy service doesn't recognize the wrong person

Third, the proxy IP selection doorway, these pits do not step on!

Delineate the focus:Don't be cheap and use free proxiesI'm not sure if you're going to be able to get a good deal on a proxy IP! Those proxy IPs that claim to be for nothing are either slow as a snail or run away in two days. ipipgo has a 3-day trial period for new users, enough to measure the results before deciding.

IV. Practical QA: the soul torture you may encounter

Q: What should I do if I still report 403 after using the proxy?
A: Check three things first: 1) whether the proxy address is spelled correctly 2) whether the authentication token has expired 3) whether the destination address requires a special protocol header

Q: What should I do if a proxy request suddenly slows down?
A: Switching line groupings in the ipipgo console is recommended forIntelligent RoutingFunction automatically selects the optimal node

Q: How can I prevent my IP from being blocked by the target website?
A: Enable ipipgo'sautomatic rotationfunction, set to change the exit IP every 5-10 minutes

Fifth, advanced skills: add some buffs to the proxy request

This can be done when a more thorough disguise is required:

fetch(proxyUrl, {
  headers: {
    'X-Forwarded-For': ipipgo.generateRandomIP(), // generate random IP headers
    'User-Agent': ipipgo.getRandomUA() // get random browser identifier
  }
})

These auxiliary methods are readily available in ipipgo's SDK, just call them directly. Especially when doing data collection, this trick can dramatically reduce the probability of being recognized.

Lastly, I would like to say that if you use a good proxy IP, you can double your development efficiency. Choose the right service provider really save too much heartache, like ipipgo can provide a complete technical program and 7 × 24 hours support, than the self-toss much stronger. What do not understand directly to their technical brother, reply faster than a takeaway boy!