Question 1

How do I convert a cURL command to JavaScript fetch() code?

Accepted Answer

Converting cURL to fetch() manually means mapping each cURL flag to its JavaScript equivalent — tedious and error-prone, especially for complex requests with multiple headers, cookies, and authentication. The mapping: cURL's -X POST becomes fetch()'s method: 'POST' option; each -H 'Header: Value' flag becomes an entry in the headers object; -d '{"key":"value"}' becomes body: JSON.stringify({key: 'value'}) with an added Content-Type: application/json header; -u user:pass becomes an Authorization: Basic base64(user:pass) header; --cookie 'name=value' becomes a Cookie header or the credentials: 'include' option; -k (insecure) has no browser equivalent since browsers enforce TLS validation. jslet's cURL-to-Fetch converter parses the cURL command string, extracts all flags, headers, method, URL, and body, and generates clean, correctly-indented fetch() code. It also outputs axios and got (Node.js) equivalents — three output formats from one paste. The tool handles quoted strings, escaped characters, and multi-line cURL commands. Paste your cURL from browser DevTools (Copy as cURL), API documentation, or a colleague's Slack message and get production-ready JavaScript instantly.

Question 2

What cURL options are supported when converting to JavaScript fetch(), axios, or got?

Accepted Answer

jslet's cURL converter supports the most commonly used cURL flags: -X / --request (HTTP method — GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS), -H / --header (request headers, each flag generates one header entry), -d / --data / --data-raw / --data-binary (request body — JSON strings, URL-encoded form data, raw text), -u / --user (Basic Authentication — parsed to an Authorization header with Base64-encoded credentials), -b / --cookie (cookies sent as a Cookie header), --compressed (Accept-Encoding: gzip header — fetch handles decompression automatically), and -L / --location (follow redirects — fetch follows redirects by default with redirect: 'follow'). Flags that have no browser fetch() equivalent are noted in the output: -k / --insecure (TLS verification bypass — browsers always verify certs), --connect-timeout (fetch has AbortController timeout but not a per-connection timeout), and -o / --output (download to file — browsers use the Download API). For Node.js users, the got output includes proxy, timeout, and retry options. The converter preserves the URL, query parameters, and URL fragments exactly as specified in the original cURL command.

Question 3

Why should I use fetch() instead of running cURL commands in production backend code?

Accepted Answer

cURL is a command-line tool designed for interactive debugging and shell scripting — it is not a programmatic HTTP client for application code. Using cURL via shell execution in backend code (Node.js child_process.exec, Python subprocess.run, PHP shell_exec) introduces critical risks: (1) Command injection — if any part of the URL, headers, or body is built from user input, an attacker can inject shell metacharacters (;, &&, |, backticks) to execute arbitrary commands on your server. (2) No structured error handling — cURL exits with a status code, but parsing the output, headers, and timing data from raw text is fragile. (3) No connection pooling — each cURL invocation opens a new TCP+TLS connection, adding 50–300ms of latency per request that native HTTP clients avoid via keep-alive pools. (4) No streaming or abort — fetch() and axios support ReadableStream bodies and AbortController cancellation. The correct approach: use cURL in your terminal to explore and debug an API, then convert the working cURL command to fetch()/axios/got code using jslet's converter. The generated JavaScript is safe to deploy: no shell injection surface, native promise-based error handling, and full access to the browser/Node.js HTTP client ecosystem.

cURL →JavaScript fetch()

🟢📖 Why Convert cURL to fetch()?