onetime

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, this one isn't naughty and extending Function.prototype.

Install

npm install onetime

Usage

import onetime from 'onetime';

let index = 0;

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

foo(); //=> 1
foo(); //=> 1
foo(); //=> 1

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

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.

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.

Similar packages

Other packages similar to onetime

once

The 'once' package is similar to 'onetime' in that it ensures a function can only be called once. The main difference is in the API and additional features that 'once' might provide, such as the ability to clear the once wrapper and allow the function to be called again.

lodash.once

Provided by the popular Lodash library, 'lodash.once' is a function that ensures a given function can only be called once. It is similar to 'onetime' but comes as part of the larger Lodash utility library, which might be preferable if you are already using Lodash in your project.