@shopify/flash-list
Version:
FlashList is a more performant FlatList replacement
78 lines • 3.24 kB
JavaScript
"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.MultiTypeAverageWindow = exports.AverageWindow = void 0;
/**
* Helper class to calculate running average of the most recent n values
*/
var AverageWindow = /** @class */ (function () {
function AverageWindow(size, startValue) {
this.nextIndex = 0;
this.inputValues = new Array(Math.max(1, size));
this.currentAverage = startValue !== null && startValue !== void 0 ? startValue : 0;
this.currentCount = startValue === undefined ? 0 : 1;
this.nextIndex = this.currentCount;
this.inputValues[0] = startValue;
}
Object.defineProperty(AverageWindow.prototype, "currentValue", {
/**
* Can be used to get the current average value
*/
get: function () {
return this.currentAverage;
},
enumerable: false,
configurable: true
});
/**
*
* @param value Add new value to the average window and updated current average
*/
AverageWindow.prototype.addValue = function (value) {
var target = this.getNextIndex();
var oldValue = this.inputValues[target];
var newCount = oldValue === undefined ? this.currentCount + 1 : this.currentCount;
this.inputValues[target] = value;
this.currentAverage =
this.currentAverage * (this.currentCount / newCount) +
(value - (oldValue !== null && oldValue !== void 0 ? oldValue : 0)) / newCount;
this.currentCount = newCount;
};
AverageWindow.prototype.getNextIndex = function () {
// starts from 0 once we reach end of the array
var newTarget = this.nextIndex;
this.nextIndex = (this.nextIndex + 1) % this.inputValues.length;
return newTarget;
};
return AverageWindow;
}());
exports.AverageWindow = AverageWindow;
var MultiTypeAverageWindow = /** @class */ (function () {
/**
* @param windowSize Size of the average window
* @param defaultValue Default value to return if no value is available
*/
function MultiTypeAverageWindow(windowSize, defaultValue) {
this.averageWindows = new Map();
this.windowSize = windowSize;
this.defaultValue = defaultValue;
}
MultiTypeAverageWindow.prototype.addValue = function (value, type) {
var averageWindow = this.averageWindows.get(type);
if (!averageWindow) {
averageWindow = new AverageWindow(this.windowSize);
this.averageWindows.set(type, averageWindow);
}
averageWindow.addValue(value);
};
MultiTypeAverageWindow.prototype.getCurrentValue = function (type) {
var _a, _b;
var averageWindow = this.averageWindows.get(type);
return (_b = (_a = averageWindow === null || averageWindow === void 0 ? void 0 : averageWindow.currentValue) !== null && _a !== void 0 ? _a : this.defaultValue) !== null && _b !== void 0 ? _b : 0;
};
MultiTypeAverageWindow.prototype.reset = function () {
this.averageWindows.clear();
};
return MultiTypeAverageWindow;
}());
exports.MultiTypeAverageWindow = MultiTypeAverageWindow;
//# sourceMappingURL=AverageWindow.js.map