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LocalQueue.js
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LocalQueue.js
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/*
* LocalQueue
* A queue implemented on top of local storage
*
* Copyright 2014, loneranger
* Licensed under the MIT license
* Supports the following methods:
* #push()
* #pop()
* #getFront()
* #getBack()
* #getAll()
* #removeAll()
*/
LocalQueue = function(key) {
if (!key) return null;
//Init
var exports = {};
var DELIMITER = String.fromCharCode(31);
//methods
function getFromLocalStorage(key) {
var storageItem = localStorage.getItem(key);
if (!storageItem || storageItem == null) {
localStorage.setItem(key, "");
return "";
}
return storageItem;
}
function stringToArray(s) {
var parseArr = [];
if (s && s != null) {
var items = s.split(DELIMITER);
items.forEach(function(item) {
try {
var parsedItem = JSON.parse(item);
parseArr.push(parsedItem);
} catch (err) {
console.error(err);
}
});
}
return parseArr;
}
/*
Push an item into the queue
*/
exports.push = function(item) {
try {
var queueString = getFromLocalStorage(key);
if (queueString == "") queueString += JSON.stringify(item);
else queueString += DELIMITER + JSON.stringify(item);
localStorage.setItem(key, queueString);
} catch (err) {
return false;
}
return true;
}
/*
Push an array of items into the queue
This operation is transactional. Either all the array items get pushed or none get pushed.
*/
exports.pushAll = function(itemArr) {
try {
if(Object.prototype.toString.call(itemArr) === '[object Array]') {
var queueString = getFromLocalStorage(key);
var tempQueueString = "";
for(var i=0; i<itemArr.length; i++){
var item = itemArr[i];
if (tempQueueString == "") tempQueueString += JSON.stringify(item);
else tempQueueString += DELIMITER + JSON.stringify(item);
}
if (queueString == "") queueString += tempQueueString;
else queueString += DELIMITER + tempQueueString;
localStorage.setItem(key, queueString);
} else return false;
} catch (err) {
return false;
}
return true;
}
/*
Pop an item from the queue
*/
exports.pop = function() {
try {
var queueString = getFromLocalStorage(key);
var firstDelimiterIndex = queueString.indexOf(DELIMITER);
if (firstDelimiterIndex > -1) {
var firstItemString = queueString.substr(0, firstDelimiterIndex);
queueString = queueString.substr(firstDelimiterIndex + 1);
localStorage.setItem(key, queueString);
return JSON.parse(firstItemString);
} else if (queueString.length > 0) {
localStorage.setItem(key, "");
return JSON.parse(queueString);
} else return null;
} catch (err) {
return null;
}
return null;
}
/*
same as Pop, only non-destructive (read-only)
*/
exports.getFront = function() {
try {
var queueString = getFromLocalStorage(key);
var firstDelimiterIndex = queueString.indexOf(DELIMITER);
if (firstDelimiterIndex > -1) {
var firstItemString = queueString.substr(0, firstDelimiterIndex);
return JSON.parse(firstItemString);
} else if (queueString.length > 0) {
return JSON.parse(queueString);
} else return null;
} catch (err) {
return null;
}
return null;
}
/*
reads the last pushed item, without delete from queue
*/
exports.getBack = function() {
try {
var queueString = getFromLocalStorage(key);
var lastDelimiterIndex = queueString.lastIndexOf(DELIMITER);
if (lastDelimiterIndex > -1) {
var lastItemString = queueString.substr(lastDelimiterIndex+1);
return JSON.parse(lastItemString);
} else if (queueString.length > 0) {
return JSON.parse(queueString);
} else return null;
} catch (err) {
return null;
}
return null;
}
/*
Get all items
*/
exports.getAll = function() {
return stringToArray(getFromLocalStorage(key));
}
/*
Remove all Items
*/
exports.removeAll = function() {
var queueString = getFromLocalStorage(key);
localStorage.setItem(key, "");
return stringToArray(queueString);
}
return exports;
}