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author | Joel Kronqvist <work.joelkronqvist@pm.me> | 2022-03-11 20:46:06 +0200 |
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committer | Joel Kronqvist <work.joelkronqvist@pm.me> | 2022-03-11 20:46:06 +0200 |
commit | 080c5819d87b933816d724a83f3bf4f1686770a7 (patch) | |
tree | 4a2ccc68b27edf7d4cbc586c932cc7542b655e19 /node_modules/once/README.md | |
parent | 5ac7049a9d30733165cc212dee308163c2a14644 (diff) | |
parent | d003b82235a9329f912522a2f70aa950dfce4998 (diff) | |
download | LYLLRuoka-080c5819d87b933816d724a83f3bf4f1686770a7.tar.gz LYLLRuoka-080c5819d87b933816d724a83f3bf4f1686770a7.zip |
Merge branch 'master' of https://github.com/JoelHMikael/FoodJS
Updating remote changes
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-rw-r--r-- | node_modules/once/README.md | 79 |
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diff --git a/node_modules/once/README.md b/node_modules/once/README.md new file mode 100644 index 0000000..1f1ffca --- /dev/null +++ b/node_modules/once/README.md @@ -0,0 +1,79 @@ +# once + +Only call a function once. + +## usage + +```javascript +var once = require('once') + +function load (file, cb) { + cb = once(cb) + loader.load('file') + loader.once('load', cb) + loader.once('error', cb) +} +``` + +Or add to the Function.prototype in a responsible way: + +```javascript +// only has to be done once +require('once').proto() + +function load (file, cb) { + cb = cb.once() + loader.load('file') + loader.once('load', cb) + loader.once('error', cb) +} +``` + +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. + +```javascript +var once = require('once') + +function load (cb) { + cb = once(cb) + var stream = createStream() + stream.once('data', cb) + stream.once('end', function () { + if (!cb.called) cb(new Error('not found')) + }) +} +``` + +## `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: + +```javascript +function greet (name, cb) { + // return is missing from the if statement + // when no name is passed, the callback is called twice + if (!name) cb('Hello anonymous') + cb('Hello ' + name) +} + +function log (msg) { + console.log(msg) +} + +// this will print 'Hello anonymous' but the logical error will be missed +greet(null, once(msg)) + +// once.strict will print 'Hello anonymous' and throw an error when the callback will be called the second time +greet(null, once.strict(msg)) +``` |