I am working on a TODO list, I'm trying to make this work with local storage. But there is a problem in my code I can't resolve.

The function getTaskArray() retrieved the, whats meant to be, array from the local storage under the key 'tasks'. If it cannot find it it created a new array instead.

The pushData() function should push the task object into the array. But I get the following error: taskArray.push is not a function.

I've attached a snippet of my code below.

Thanks in advance for your help!

var taskArray;
function getTaskArray() {
    var taskArrayString = localStorage.getItem("tasks");
    if (taskArrayString !== null && typeof taskArrayString === "string") {
        taskArray = taskArrayString;
        console.log("Succesfully retrieved 'tasks' and contents.");
    } else {
        console.log("Succesfully retrieved 'tasks', contents were not a string or held no contents. Contents of 'tasks' reset to empty array");
        var emptyArray = JSON.stringify(new Array());
        localStorage.setItem("tasks", emptyArray);
        taskArray = localStorage.getItem("tasks");
    };
};

var taskString;

function pushData() {
    taskString = JSON.stringify(taskObject);
    taskArray = taskArray.push(taskString);
};

Update:

The plete version of my code:

// All functions
var taskFromHtml;
var priorityFromHtml;

function getTaskInput() {
    try {
        taskFromHtml = $("#taak").val();
        priorityFromHtml = $("#prioriteit").val();
        console.log("Succesfully retrieved data. Task: " + taskFromHtml + ". Priority: " + priorityFromHtml + ".");
    } catch(e) {
        console.log("Failed to retrieve data, unexpecter error.");
    };
};

var taskObject;
function taskToObject() {
    taskObject = {
        task: taskFromHtml,
        priority: priorityFromHtml,
        finished: false
    }; 
};

var taskArray;
function getTaskArray() {
    var taskArrayString = localStorage.getItem("tasks");
    if (taskArrayString !== null && typeof taskArrayString === "string") {
        taskArray = JSON.parse(taskArrayString); // <------
        console.log("Succesfully retrieved 'tasks' and contents.");
    } else {
        console.log("Succesfully retrieved 'tasks', contents were not a string or held no contents. Contents of 'tasks' reset to empty array");
        var emptyArray = JSON.stringify(new Array());
        localStorage.setItem("tasks", emptyArray);
        taskArray = localStorage.getItem("tasks");
        taskArray = JSON.parse(taskArray); // <------
    };
};

var taskString;

function pushData() {
    taskString = JSON.stringify(taskObject);
    taskArray = taskArray.push(taskString);
};

And it's HTML:

  <form id="todoInsert" action="#">
        <input type="text" name="task" id="taak">
        <select id="prioriteit">
            <option value="1">1</option>
            <option value="2">2</option>
            <option value="3">3</option>
            <option value="4">4</option>
            <option value="5">5</option>
        </select>

        <input type="submit" id="formSubmit">
    </form>
    <div id="addItem">+</div>

I am working on a TODO list, I'm trying to make this work with local storage. But there is a problem in my code I can't resolve.

The function getTaskArray() retrieved the, whats meant to be, array from the local storage under the key 'tasks'. If it cannot find it it created a new array instead.

The pushData() function should push the task object into the array. But I get the following error: taskArray.push is not a function.

I've attached a snippet of my code below.

Thanks in advance for your help!

var taskArray;
function getTaskArray() {
    var taskArrayString = localStorage.getItem("tasks");
    if (taskArrayString !== null && typeof taskArrayString === "string") {
        taskArray = taskArrayString;
        console.log("Succesfully retrieved 'tasks' and contents.");
    } else {
        console.log("Succesfully retrieved 'tasks', contents were not a string or held no contents. Contents of 'tasks' reset to empty array");
        var emptyArray = JSON.stringify(new Array());
        localStorage.setItem("tasks", emptyArray);
        taskArray = localStorage.getItem("tasks");
    };
};

var taskString;

function pushData() {
    taskString = JSON.stringify(taskObject);
    taskArray = taskArray.push(taskString);
};

Update:

The plete version of my code:

// All functions
var taskFromHtml;
var priorityFromHtml;

function getTaskInput() {
    try {
        taskFromHtml = $("#taak").val();
        priorityFromHtml = $("#prioriteit").val();
        console.log("Succesfully retrieved data. Task: " + taskFromHtml + ". Priority: " + priorityFromHtml + ".");
    } catch(e) {
        console.log("Failed to retrieve data, unexpecter error.");
    };
};

var taskObject;
function taskToObject() {
    taskObject = {
        task: taskFromHtml,
        priority: priorityFromHtml,
        finished: false
    }; 
};

var taskArray;
function getTaskArray() {
    var taskArrayString = localStorage.getItem("tasks");
    if (taskArrayString !== null && typeof taskArrayString === "string") {
        taskArray = JSON.parse(taskArrayString); // <------
        console.log("Succesfully retrieved 'tasks' and contents.");
    } else {
        console.log("Succesfully retrieved 'tasks', contents were not a string or held no contents. Contents of 'tasks' reset to empty array");
        var emptyArray = JSON.stringify(new Array());
        localStorage.setItem("tasks", emptyArray);
        taskArray = localStorage.getItem("tasks");
        taskArray = JSON.parse(taskArray); // <------
    };
};

var taskString;

function pushData() {
    taskString = JSON.stringify(taskObject);
    taskArray = taskArray.push(taskString);
};

And it's HTML:

  <form id="todoInsert" action="#">
        <input type="text" name="task" id="taak">
        <select id="prioriteit">
            <option value="1">1</option>
            <option value="2">2</option>
            <option value="3">3</option>
            <option value="4">4</option>
            <option value="5">5</option>
        </select>

        <input type="submit" id="formSubmit">
    </form>
    <div id="addItem">+</div>

• javascript
• html
• arrays
• json
• local-storage

• Where's taskObject defined? – hindmost Commented Nov 19, 2015 at 8:55
• @BasvanStein it is a little further in the code, have not yet started debugging that. But there is a line of code in the snippet above: localStorage.setItem("tasks", []); – Demiën Drost Commented Nov 19, 2015 at 9:02
• @DemiënDrost ok, be sure to do JSON.stringify when setting the localStorage as well, see my updated answer for your fixed code. – Niki van Stein Commented Nov 19, 2015 at 9:16
• @hindmost var taskObject; function taskToObject() { taskObject = { task: taskFromHtml, priority: priorityFromHtml, finished: false }; }; – Demiën Drost Commented Nov 19, 2015 at 9:16

2 Answers 2

You get the error because you try to perform the push function on a String instead of an array.

When you get the String from the localStorage you need to parse it using JSON.parse().

taskArray = JSON.parse( localStorage.getItem("tasks"));

And also when your receive is succesfully in the if part:

taskArray = JSON.parse(taskArrayString);

Your plete working code would be:

var taskArray;
function getTaskArray() {
    var taskArrayString = localStorage.getItem("tasks");
    if (taskArrayString !== null && typeof taskArrayString === "string") {
        taskArray = JSON.parse(taskArrayString); // <------
        console.log("Succesfully retrieved 'tasks' and contents.");
    } else {
        console.log("Succesfully retrieved 'tasks', contents were not a string or held no contents. Contents of 'tasks' reset to empty array");
        var emptyArray = JSON.stringify(new Array());
        localStorage.setItem("tasks", emptyArray);
        taskArray = localStorage.getItem("tasks");
        taskArray = JSON.parse(taskArray); // <------
    };
};

var taskString;

function pushData() {
    taskString = JSON.stringify(taskObject);
    taskArray.push(taskString); // <----- !No need to assign there.
};

Here you can see a working JsFiddle: https://jsfiddle/txvp9uwc/2/

You can only save the data in string format in the local storage. You can not save, dates, numbers or any other data types. For that you can serialize and deserialize your data as JSON string and then persist the data.

There are some awesome wrapper libraries available which do that for you: https://github./nbubna/store or https://github./marcuswestin/store.js/

Update

You need to deserialize your string after retrieval before using it:

var taskArrayString = localStorage.getItem("tasks");
if (taskArrayString !== null && typeof taskArrayString === "string") {
    taskArray = JSON.parse(taskArrayString);   // deserializing here
    console.log("Succesfully retrieved 'tasks' and contents.");
}