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  # onetime [![Build Status](https://travis-ci.org/sindresorhus/onetime.svg?branch=master)](https://travis-ci.org/sindresorhus/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 extending `Function.prototype`.*
  
  
  ## Install
  
  ```
  $ npm install --save onetime
  ```
  
  
  ## Usage
  
  ```js
  let i = 0;
  
  const foo = onetime(() => i++);
  
  foo(); //=> 0
  foo(); //=> 0
  foo(); //=> 0
  ```
  
  ```js
  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`
  
  Function that should only be called once.
  
  #### options
  
  Type: `Object`
  
  ##### throw
  
  Type: `boolean`<br>
  Default: `false`
  
  Throw an error when called more than once.
  
  
  ## License
  
  MIT © [Sindre Sorhus](https://sindresorhus.com)