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author | Michaël Zasso <targos@protonmail.com> | 2017-12-22 16:53:42 +0100 |
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committer | Michaël Zasso <targos@protonmail.com> | 2018-01-11 09:48:05 +0100 |
commit | 3dc30632755713179f345f4af024bd904c6162d0 (patch) | |
tree | f28c4f6dd6dfc5992edf301449d1a371d229755b /tools/node_modules/eslint/node_modules/once/README.md | |
parent | a2c7085dd4a8e60d1a47572aca8bb6fcb7a32f88 (diff) | |
download | android-node-v8-3dc30632755713179f345f4af024bd904c6162d0.tar.gz android-node-v8-3dc30632755713179f345f4af024bd904c6162d0.tar.bz2 android-node-v8-3dc30632755713179f345f4af024bd904c6162d0.zip |
tools: move eslint from tools to tools/node_modules
This is required because we need to add the babel-eslint dependency
and it has to be able to resolve "eslint".
babel-eslint is required to support future ES features such as async
iterators and import.meta.
Refs: https://github.com/nodejs/node/pull/17755
PR-URL: https://github.com/nodejs/node/pull/17820
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Diffstat (limited to 'tools/node_modules/eslint/node_modules/once/README.md')
-rw-r--r-- | tools/node_modules/eslint/node_modules/once/README.md | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/node_modules/once/README.md b/tools/node_modules/eslint/node_modules/once/README.md new file mode 100644 index 0000000000..1f1ffca933 --- /dev/null +++ b/tools/node_modules/eslint/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)) +``` |