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update throttle and debounce description based on lodash docs #30

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update throttle and debounce description based on lodash docs #30

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6f6c688
update throttle and debounce description based on lodash docs; add ad…
webkonstantin Mar 23, 2016
7e23f97
update README
webkonstantin Mar 23, 2016
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30 changes: 22 additions & 8 deletions README.md
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Expand Up @@ -87,10 +87,24 @@ Options:
Instances of `{path}` or `{event}` within the command
will be replaced by the corresponding values from the
chokidar event.
-d, --debounce Debounce timeout in ms for executing command
[default: 400]
-t, --throttle Throttle timeout in ms for executing command
[default: 0]
-d, --debounce Delays command execution until after specified ms have
elapsed since the last time the debounced command was
executed [default: 400]
--debounce-leading Specify executing on the leading edge of the timeout
[boolean] [default: false]
--debounce-max-wait The maximum time command is allowed to be delayed
before it is executed
--debounce-trailing Specify executing on the trailing edge of the timeout
[boolean] [default: true]
-t, --throttle Only execute command at most once per every specified
ms. Note: If leading and trailing options are true,
command is executed on the trailing edge of the
timeout only if the the throttled command is invoked
more than once during the timeout [default: 0]
--throttle-leading Specify executing on the leading edge of the timeout
[boolean] [default: true]
--throttle-trailing Specify executing on the trailing edge of the timeout
[boolean] [default: true]
-s, --follow-symlinks When not set, only the symlinks themselves will be
watched for changes instead of following the link
references and bubbling events through the links path
Expand All @@ -106,10 +120,10 @@ Options:
of fs.watch. This might lead to high CPU utilization.
It is typically necessary to set this to true to
successfully watch files over a network, and it may be
necessary to successfully watch files in other non-
standard situations [boolean] [default: false]
--poll-interval Interval of file system polling. Effective when --
polling is set [default: 100]
necessary to successfully watch files in other
non-standard situations [boolean] [default: false]
--poll-interval Interval of file system polling. Effective when
--polling is set [default: 100]
--poll-interval-binary Interval of file system polling for binary files.
Effective when --polling is set [default: 300]
--verbose When set, output is more verbose and human readable.
Expand Down
59 changes: 55 additions & 4 deletions index.js
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Expand Up @@ -16,7 +16,12 @@ var EVENT_DESCRIPTIONS = {

var defaultOpts = {
debounce: 400,
debounceLeading: false,
debounceMaxWait: undefined,
debounceTrailing: true,
throttle: 0,
throttleLeading: true,
throttleTrailing: true,
followSymlinks: false,
ignore: null,
polling: false,
Expand Down Expand Up @@ -54,15 +59,44 @@ var argv = require('yargs')
.option('d', {
alias: 'debounce',
default: defaultOpts.debounce,
describe: 'Debounce timeout in ms for executing command',
describe: 'Delays command execution until after specified ms have ' +
'elapsed since the last time the debounced command was executed',
type: 'number'
})
.option('debounce-leading', {
default: defaultOpts.debounceLeading,
describe: 'Specify executing on the leading edge of the timeout',
type: 'boolean'
})
.option('debounce-max-wait', {
default: defaultOpts.debounceMaxWait,
describe: 'The maximum time command is allowed to be delayed before it is executed',
type: 'number'
})
.option('debounce-trailing', {
default: defaultOpts.debounceTrailing,
describe: 'Specify executing on the trailing edge of the timeout',
type: 'boolean'
})
.option('t', {
alias: 'throttle',
default: defaultOpts.throttle,
describe: 'Throttle timeout in ms for executing command',
describe: 'Only execute command at most once per every specified ms. ' +
'Note: If leading and trailing options are true, command is ' +
'executed on the trailing edge of the timeout only if the the ' +
'throttled command is invoked more than once during the timeout',
type: 'number'
})
.option('throttle-leading', {
default: defaultOpts.throttleLeading,
describe: 'Specify executing on the leading edge of the timeout',
type: 'boolean'
})
.option('throttle-trailing', {
default: defaultOpts.throttleTrailing,
describe: 'Specify executing on the trailing edge of the timeout',
type: 'boolean'
})
.option('s', {
alias: 'follow-symlinks',
default: defaultOpts.followSymlinks,
Expand Down Expand Up @@ -139,8 +173,14 @@ function startWatching(opts) {
var chokidarOpts = createChokidarOpts(opts);
var watcher = chokidar.watch(opts.patterns, chokidarOpts);

var throttledRun = _.throttle(run, opts.throttle);
var debouncedRun = _.debounce(throttledRun, opts.debounce);
var throttledRun = _.throttle(run, opts.throttle, {
leading: opts.throttleLeading,
trailing: opts.throttleTrailing
});

var debounceOpts = createDebounceOpts(opts);
var debouncedRun = _.debounce(throttledRun, opts.debounce, debounceOpts);

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what happens here when you pass the throttled function to debounce?

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Passing throttled function to debounce was not introduced by me in this PR, but in this commit by ElliotChong and merged before
kimmobrunfeldt/chokidar-cli@609228b#diff-168726dbe96b3ce427e7fedce31bb0bcR142

I believe it combines debounce (execute after specified ms have elapsed since the last time the debounced function was called) and throttle (do not execute more than once in specified timeframe) behaviour as you would expect without any negative side-effects.

watcher.on('all', function(event, path) {
var description = EVENT_DESCRIPTIONS[event] + ':';

Expand Down Expand Up @@ -191,6 +231,17 @@ function createChokidarOpts(opts) {
return chokidarOpts;
}

function createDebounceOpts(opts) {
var debounceOpts = {
leading: opts.debounceLeading,
trailing: opts.debounceTrailing
};

if (opts.debounceMaxWait) debounceOpts.maxWait = opts.debounceMaxWait;

return debounceOpts;
}

// Takes string or array of strings
function _resolveIgnoreOpt(ignoreOpt) {
if (!ignoreOpt) {
Expand Down