Ensures that a string starts with the given prefix, if it does not already.
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README.md

with-prefix

Ensures that a string starts with the given prefix, if it does not already. Also comes with a couple of extra utilities for common use cases.

Usage

Install with yarn add with-prefix.

In your code:

import withPrefix from 'with-prefix';

withPrefix('hello-world.com', 'www.'); // => www.hello-world.com
withPrefix('www.hello-world.com', 'www.'); // => www.hello-world.com

You can also use the startsWith function which checks if the prefix exists.

import { startsWith } from 'with-prefix';

startsWith('hello-world.com', 'www.'); // => false
startsWith('www.hello-world.com', 'www.'); // => true

Utilities

The library also comes with the functions withHTTP and withTell. If you have an idea for some other common utilities with this pattern, send a Pull Request, or fork this repo and publish your own package.

withHTTP

If the provided string stats with http:// or https:// then it is left as is. If not, then one of the two defaults based on the second argument.

import { withHTTP } from 'with-prefix';

// signature: withHTPP = (target: String, useTLS: Boolean): String

// prefix based on the 2nd argument
withHTTP('hello-world.com', false); // => http://hello-world.com
withHTTP('hello-world.com', true); // => https://hello-world.com

// valid input is left alone
withHTTP('http://hello-world.com', false); // => http://hello-world.com
withHTTP('http://hello-world.com', true); // => http://hello-world.com

// valid input is left alone
withHTTP('https://hello-world.com', false); // => https://hello-world.com
withHTTP('https://hello-world.com', true); // => https://hello-world.com

withTell

import { withTell } from 'with-prefix';

// signature: withTell = (target: String): String


// prefix when no tell://
withTell('344-31-221'); // => tell://344-31-221

// valid input is left alone
withTell('tell://344-31-221'); // => tell://344-31-221