Source: oncetriggers.js

/*
 * GDevelop JS Platform
 * Copyright 2013-2016 Florian Rival ([email protected]). All rights reserved.
 * This project is released under the MIT License.
 */

/**
 * OnceTriggers is used to store the status of the conditions "Trigger once",
 * that are used in events to have conditions that are only valid for one frame in a row.
 *
 * @memberof gdjs
 * @class OnceTriggers
 * @constructor
 */
gdjs.OnceTriggers = function()
{
    this._onceTriggers = {};
    this._lastFrameOnceTrigger = {};
};

/**
 * To be called when events begin so that "Trigger once" conditions
 * are properly handled.
 */
gdjs.OnceTriggers.prototype.startNewFrame = function() {
    this._clearObject(this._lastFrameOnceTrigger);
    for (var k in this._onceTriggers) {
        if (this._onceTriggers.hasOwnProperty(k)) {
            this._lastFrameOnceTrigger[k] = this._onceTriggers[k];
            delete this._onceTriggers[k];
        }
    }
};

/**
 * Used by "Trigger once" conditions: return true only if
 * this method was not called with the same identifier during the last frame.
 * @param triggerId The identifier of the "Trigger once" condition.
 */
gdjs.OnceTriggers.prototype.triggerOnce = function(triggerId) {
    this._onceTriggers[triggerId] = true;

    return !this._lastFrameOnceTrigger.hasOwnProperty(triggerId);
};

gdjs.OnceTriggers.prototype._clearObject = function(obj) {
    for (var k in obj) {
        if (obj.hasOwnProperty(k)) {
            delete obj[k];
        }
    }
};