Local Storage Error on array push

Question

I'm doing some tests with local storage. In my tests with array, i was stuck in array part (push).

What i've done:

if (localStorage.myArray) {
    localStorage.myArray.push("Green");
} else {
    localStorage.myArray = ["Red", "Blue"];
}

This returns an error:

Uncaught TypeError: localStorage.myArray.push is not a function

I know the localstorage itens are always string, but i don't know how this works in an array.

http://stackoverflow.com/questions/2010892/storing-objects-in-html5-localstorage — KJYe.Name, Jul 14 '15 at 14:53
Is `localStorage.myArray` really an Array? Try typing it in the console or looking at `localStorage.myArray.constructor` — Domino, Jul 14 '15 at 14:54

score 5 · Accepted Answer · answered Jul 14 '15 at 14:52

Since localStorage only takes strings, you would have to convert your arrays to JSON strings using JSON.stringify. Parse the JSON strings to array while performing further operations on the "arrays". Something like this

if (localStorage.myArray) {
    var myArray = JSON.parse(localStorage.myArray);
    myArray.push("Green");
    localStorage.myArray = JSON.stringify(myArray);
} else {
    localStorage.myArray = JSON.stringify(["Red", "Blue"]);
}

Hum, the JSON conversion is what i needed. Thank you. – reidark Jul 14 '15 at 16:28 — reidark, Jul 14 '15 at 16:28

score 0 · Answer 2 · answered Jul 14 '15 at 14:54

0

if (localStorage.myArray) {
    var myArray = localStorage.myArray.split(',');
    myArray.push("Green");
    localStorage.myArray = myArray;
} else {
   localStorage.myArray = ["Red", "Blue"];
}

answered Jul 14 '15 at 14:54

Darx

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this works fine but what if the array was `["Hello, Red", "Hello, Green"]` – Dhiraj Jul 14 '15 at 14:56
1

Then your solution would fit better. But in this specific use case split is the fastest way. – Darx Jul 14 '15 at 15:00

Local Storage Error on array push

2 Answers2