threaded-lock/dist/index.js

A threaded lock for Javascript written in Typescript

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var interval = 40;
var default_1 = (function () {
    function default_1(name, timeout, seed) {
        if (timeout === void 0) { timeout = 5000; }
        this.name = name;
        this.timeout = timeout;
        this.seed = seed;
        if (!this.seed) {
            this.seed = Math.random();
        }
        this.setExpiration();
    }
    default_1.prototype.lock = function () {
        var _this = this;
        return new Promise(function (res, rej) {
            _this.lockCheck = function () {
                var doublecheck = _this.read();
                if (doublecheck && doublecheck.expires > Date.now()) {
                    return;
                }
                if (_this.unlock()) {
                    res();
                }
            };
            var existing = _this.read();
            if (!existing || existing.expires < Date.now()) {
                _this.write();
                setTimeout(function () {
                    var doublecheck = _this.read();
                    var claimed = false;
                    if (doublecheck) {
                        if (doublecheck.seed === _this.seed || doublecheck.expires < Date.now()) {
                            claimed = true;
                            _this.claimLockFlow(res, rej);
                            return;
                        }
                    }
                    if (claimed) {
                        return;
                    }
                    _this.waitOnLockFlow();
                }, interval);
                return;
            }
            _this.waitOnLockFlow();
        });
    };
    default_1.prototype.unlock = function () {
        var lock = this.read();
        if (lock && lock.seed !== this.seed && lock.expires > Date.now()) {
            return false;
        }
        clearInterval(this.heartbeat);
        window.removeEventListener("storage", this.lockCheck);
        localStorage.removeItem(this.name);
        return true;
    };
    default_1.prototype.read = function () {
        var res = localStorage.getItem(this.name);
        if (!res) {
            return undefined;
        }
        try {
            return JSON.parse(res);
        }
        catch (e) {
            return undefined;
        }
    };
    default_1.prototype.write = function () {
        localStorage.setItem(this.name, JSON.stringify(this));
    };
    default_1.prototype.setExpiration = function () {
        this.expires = Date.now() + this.timeout;
    };
    default_1.prototype.claimLockFlow = function (res, rej) {
        var _this = this;
        this.setExpiration();
        window.removeEventListener("storage", this.lockCheck);
        this.heartbeat = setInterval(function () {
            _this.setExpiration();
            _this.write();
        }, this.timeout - this.timeout / 2);
        res();
    };
    default_1.prototype.waitOnLockFlow = function () {
        var _this = this;
        window.addEventListener("storage", this.lockCheck);
        this.heartbeat = setInterval(function () {
            _this.lockCheck();
        }, this.timeout);
    };
    return default_1;
}());
exports.default = default_1;