Bernt
58ca4e68db
- Go backend API with full CRUD for all modules (CRM, Sales, Finance, HR, Legal, Marketing, Support, Purchase, Inventory, Projects, Automation, Analytics) - Rust analytics service with parallel report generation - C runtime with POSIX shared memory IPC - PostgreSQL schema with 30+ tables, full migrations - Redis cache, sessions, pub/sub - Kafka event streaming with Zookeeper - WebSocket hub for real-time updates - Automation engine with cron jobs, workflows, event triggers - JWT authentication, multi-tenant from start - Docker Compose with all services - Nginx reverse proxy with rate limiting - Integration tests passing - Feature gap analysis against Fortnox/Odoo/Visma Refs: BOC-001
80 lines
1.7 KiB
Markdown
80 lines
1.7 KiB
Markdown
# once
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Only call a function once.
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## usage
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```javascript
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var once = require('once')
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function load (file, cb) {
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cb = once(cb)
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loader.load('file')
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loader.once('load', cb)
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loader.once('error', cb)
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}
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```
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Or add to the Function.prototype in a responsible way:
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```javascript
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// only has to be done once
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require('once').proto()
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function load (file, cb) {
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cb = cb.once()
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loader.load('file')
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loader.once('load', cb)
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loader.once('error', cb)
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}
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```
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Ironically, the prototype feature makes this module twice as
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complicated as necessary.
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To check whether you function has been called, use `fn.called`. Once the
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function is called for the first time the return value of the original
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function is saved in `fn.value` and subsequent calls will continue to
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return this value.
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```javascript
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var once = require('once')
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function load (cb) {
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cb = once(cb)
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var stream = createStream()
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stream.once('data', cb)
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stream.once('end', function () {
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if (!cb.called) cb(new Error('not found'))
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})
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}
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```
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## `once.strict(func)`
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Throw an error if the function is called twice.
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Some functions are expected to be called only once. Using `once` for them would
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potentially hide logical errors.
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In the example below, the `greet` function has to call the callback only once:
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```javascript
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function greet (name, cb) {
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// return is missing from the if statement
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// when no name is passed, the callback is called twice
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if (!name) cb('Hello anonymous')
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cb('Hello ' + name)
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}
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function log (msg) {
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console.log(msg)
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}
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// this will print 'Hello anonymous' but the logical error will be missed
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greet(null, once(msg))
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// once.strict will print 'Hello anonymous' and throw an error when the callback will be called the second time
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greet(null, once.strict(msg))
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```
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