https://github.com/sindresorhus/onetime

Ensure a function is only called once
https://github.com/sindresorhus/onetime

Last synced: about 1 month ago
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Ensure a function is only called once

• Host: GitHub
• URL: https://github.com/sindresorhus/onetime
• Owner: sindresorhus
• License: mit
• Created: 2013-12-01T22:19:23.000Z (almost 11 years ago)
• Default Branch: main
• Last Pushed: 2023-11-05T20:42:05.000Z (about 1 year ago)
• Last Synced: 2024-04-14T09:53:10.957Z (7 months ago)
• Language: JavaScript
• Homepage:
• Size: 39.1 KB
• Stars: 157
• Watchers: 8
• Forks: 14
• Open Issues: 1
• Metadata Files:
  • Readme: readme.md
  • Funding: .github/funding.yml
  • License: license
  • Security: .github/security.md

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README

        
# onetime

> Ensure a function is only called once

When called multiple times it will return the return value from the first call.

*Unlike the module [once](https://github.com/isaacs/once), this one isn't naughty and extending `Function.prototype`.*

## Install

```sh

npm install onetime

```

## Usage

```js

import onetime from 'onetime';

let index = 0;

const foo = onetime(() => ++index);

foo(); //=> 1

foo(); //=> 1

foo(); //=> 1

onetime.callCount(foo); //=> 3

```

```js

import onetime from 'onetime';

const foo = onetime(() => {}, {throw: true});

foo();

foo();

//=> Error: Function `foo` can only be called once

```

## API

### onetime(fn, options?)

Returns a function that only calls `fn` once.

#### fn

Type: `Function`

The function that should only be called once.

#### options

Type: `object`

##### throw

Type: `boolean`\

Default: `false`

Throw an error when called more than once.

### onetime.callCount(fn)

Returns a number representing how many times `fn` has been called.

Note: It throws an error if you pass in a function that is not wrapped by `onetime`.

```js

import onetime from 'onetime';

const foo = onetime(() => {});

foo();

foo();

foo();

console.log(onetime.callCount(foo));

//=> 3

```

#### fn

Type: `Function`

The function to get call count from.