74 lines
2.4 KiB
JavaScript
74 lines
2.4 KiB
JavaScript
/*
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Copyright 2016 OpenMarket Ltd
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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/**
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* 'debounces' a function to only execute every n milliseconds.
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* Useful when react-sdk gets many, many events but only wants
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* to update the interface once for all of them.
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*
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* Note that the function must not take arguments, since the args
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* could be different for each invocarion of the function.
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*
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* The returned function has a 'cancelPendingCall' property which can be called
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* on unmount or similar to cancel any pending update.
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*/
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module.exports = function(f, minIntervalMs) {
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this.lastCall = 0;
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this.scheduledCall = undefined;
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const self = this;
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const wrapper = function() {
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const now = Date.now();
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if (self.lastCall < now - minIntervalMs) {
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f.apply(this);
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// get the time again now the function has finished, so if it
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// took longer than the delay time to execute, it doesn't
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// immediately become eligible to run again.
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self.lastCall = Date.now();
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} else if (self.scheduledCall === undefined) {
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self.scheduledCall = setTimeout(
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() => {
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self.scheduledCall = undefined;
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f.apply(this);
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// get time again as per above
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self.lastCall = Date.now();
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},
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(self.lastCall + minIntervalMs) - now,
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);
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}
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};
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// add the cancelPendingCall property
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wrapper.cancelPendingCall = function() {
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if (self.scheduledCall) {
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clearTimeout(self.scheduledCall);
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self.scheduledCall = undefined;
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}
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};
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// make sure that cancelPendingCall is copied when react rebinds the
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// wrapper
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const _bind = wrapper.bind;
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wrapper.bind = function() {
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const rebound = _bind.apply(this, arguments);
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rebound.cancelPendingCall = wrapper.cancelPendingCall;
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return rebound;
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};
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return wrapper;
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};
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