How do you handle errors in an API request (client-side)?

Anubhav Sharma 988 06 Nov 2025

How do you handle errors in an API request (client-side)?

1 Answers

ICSM Computer 23 Nov 2025

When calling an API from the client side (or from Python), errors will occur — network failures, invalid parameters, server-side crashes, authentication issues, etc.

The key is to catch those failures and respond safely instead of letting the code crash.

Client-side (Example using JavaScript `fetch`)

fetch() does NOT throw an error for HTTP errors (like 400 or 500) — it only throws for network failures.
So you must check response.ok.

async function callApi() {
  try {
    const res = await fetch("https://api.example.com/data", {
      method: "GET",
    });

    // HTTP error (400–599)
    if (!res.ok) {
      const errorBody = await res.text(); // or res.json() if guaranteed JSON
      throw new Error(`API Error: ${res.status} ${res.statusText} - ${errorBody}`);
    }

    const data = await res.json();
    console.log("Success:", data);
  }
  catch (err) {
    // Network error, timeout, CORS failure, etc.
    console.error("Request failed:", err.message);
    alert("Something went wrong. Please try again.");
  }
}

Optional advanced error types

You can categorize errors:

catch(err) {
  if (err.message.includes("Failed to fetch")) {
    console.log("Network or CORS issue");
  } else if (err.message.includes("401")) {
    console.log("Not authorized, redirect login");
  } else {
    console.log("Unexpected:", err);
  }
}

Handling API errors in Python

When using requests, you can:

Basic pattern

import requests

try:
    r = requests.get("https://api.example.com/data", timeout=10)
    r.raise_for_status()  # raises HTTPError for 4xx / 5xx responses
    data = r.json()
    print("Success:", data)

except requests.exceptions.HTTPError as e:
    print("API returned error:", r.status_code, r.text)

except requests.exceptions.ConnectionError:
    print("Network problem (DNS, refused connection, etc.)")

except requests.exceptions.Timeout:
    print("Request timed out")

except requests.exceptions.RequestException as e:
    print("Unexpected error:", e)

Full reusable wrapper (recommended)

import requests

def api_call(url, method="get", **kwargs):
    try:
        r = requests.request(method, url, timeout=10, **kwargs)
        r.raise_for_status()
        return {"success": True, "data": r.json()}
    except requests.exceptions.RequestException as e:
        return {"success": False, "error": str(e)}

result = api_call("https://api.example.com/data")
if result["success"]:
    print(result["data"])
else:
    print("API failed:", result["error"])

General error-handling principles (both JS + Python)

Type of failure	Example	What to do
Network errors	Internet down, DNS failure	Retry or show a message
Timeout	Server too slow	Retry or cancel action
HTTP error	400, 401, 404, 500	Show user-friendly message based on status
Invalid JSON	Server returned HTML instead of JSON	Add fallback and log
Authentication error	Token expired	Refresh token or redirect to login

Quick summary

Language	Error handling
JavaScript (`fetch`)	`try/catch` + check `response.ok`
Python (`requests`)	`try/except` + `raise_for_status()`

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