npmpackage.info

Gathering detailed insights and metrics for once

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TypeScript definitions for once

Gathering detailed insights and metrics for once

once - 1.4.0 | npmpackage.info

once

Run a function exactly one time

1.4.0

222

ISC

JavaScript

11,507,750,895 2.6

Installations

npm install once

Developer Guide

BETA

Typescript

No

Module System

CommonJS

Node Version

6.5.0

NPM Version

3.10.7 Pull Requests

Open

0

Total

13

Closed

10

Merged

3

Issues

Open

2

Total

4

Closed

2

Releases

Unable to fetch releases

Languages

JavaScript

JavaScript (100%)

Developer

isaacs

Download Statistics

Total Downloads

11,507,750,895

Last Day

10,899,182

Last Week

60,529,966

Last Month

255,360,202

Last Year

2,701,730,242

GitHub Statistics

ISC License

222 Stars

24 Commits

29 Forks

7 Watchers

7 Branches

6 Contributors

Updated on Aug 29, 2024

Maintainers

View All 6 Contributors

Package Meta Information

Latest Version

1.4.0

Package Id

once@1.4.0

Size

1.93 kB

NPM Version

3.10.7

Node Version

6.5.0

Published on

Sep 06, 2016

Total Downloads

Cumulative downloads

Total Downloads

11,507,750,895

Last Day

45.4%

10,899,182

Compared to previous day

Last Week

6.3%

60,529,966

Compared to previous week

Last Month

-1.7%

255,360,202

Compared to previous month

Last Year

15%

2,701,730,242

Compared to previous year

Weekly Downloads

Monthly Downloads

Yearly Downloads

Dependencies

wrappy

Dev Dependencies

tap

once

Only call a function once.

usage

1var once = require('once')
2
3function load (file, cb) {
4  cb = once(cb)
5  loader.load('file')
6  loader.once('load', cb)
7  loader.once('error', cb)
8}

Or add to the Function.prototype in a responsible way:

1// only has to be done once
2require('once').proto()
3
4function load (file, cb) {
5  cb = cb.once()
6  loader.load('file')
7  loader.once('load', cb)
8  loader.once('error', cb)
9}

Ironically, the prototype feature makes this module twice as complicated as necessary.

To check whether you function has been called, use fn.called. Once the function is called for the first time the return value of the original function is saved in fn.value and subsequent calls will continue to return this value.

1var once = require('once')
2
3function load (cb) {
4  cb = once(cb)
5  var stream = createStream()
6  stream.once('data', cb)
7  stream.once('end', function () {
8    if (!cb.called) cb(new Error('not found'))
9  })
10}

`once.strict(func)`

Throw an error if the function is called twice.

Some functions are expected to be called only once. Using once for them would potentially hide logical errors.

In the example below, the greet function has to call the callback only once:

1function greet (name, cb) {
2  // return is missing from the if statement
3  // when no name is passed, the callback is called twice
4  if (!name) cb('Hello anonymous')
5  cb('Hello ' + name)
6}
7
8function log (msg) {
9  console.log(msg)
10}
11
12// this will print 'Hello anonymous' but the logical error will be missed
13greet(null, once(msg))
14
15// once.strict will print 'Hello anonymous' and throw an error when the callback will be called the second time
16greet(null, once.strict(msg))

No vulnerabilities found.

10

Binary-Artifacts

Determines if the project has generated executable (binary) artifacts in the source repository.

10

Dangerous-Workflow

Determines if the project's GitHub Action workflows avoid dangerous patterns.

10

License

Determines if the project has defined a license.

1

Code-Review

Determines if the project requires human code review before pull requests (aka merge requests) are merged.

0

Maintained

Determines if the project is "actively maintained".

0

Pinned-Dependencies

Determines if the project has declared and pinned the dependencies of its build process.

0

Token-Permissions

Determines if the project's workflows follow the principle of least privilege.

0

CII-Best-Practices

Determines if the project has an OpenSSF (formerly CII) Best Practices Badge.

0

Fuzzing

Determines if the project uses fuzzing.

0

Branch-Protection

Determines if the default and release branches are protected with GitHub's branch protection settings.

0

Security-Policy

Determines if the project has published a security policy.

0

SAST

Determines if the project uses static code analysis.

0

Vulnerabilities

Determines if the project has open, known unfixed vulnerabilities.

Score

2.6

/10

Last Scanned on 2025-05-05

The Open Source Security Foundation is a cross-industry collaboration to improve the security of open source software (OSS). The Scorecard provides security health metrics for open source projects.

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