Storing Arrays with String Keys in LocalStorage using JavaScript

Question

Storing Arrays with String Keys in LocalStorage using JavaScript

When attempting to save an array in localStorage, the values associated with String keys seem to disappear.

Here's an example:

var myArray = [];

myArray["key1"] = "value1";
myArray[123] = "value2";

Initially, everything seems to work fine and the expected output is attained:

myArray["key1"] => value1
myArray[123] => value2

However, when trying to store the array using this method:

localStorage.setItem('myStoredArray',JSON.stringify(myArray));
var myArray = JSON.parse(localStorage.getItem('myStoredArray'));

The result no longer includes the value linked to a String Key:

myArray["key1"] => undefined
myArray[123] => value2

Is there something incorrect in my approach? Should this be working as expected, or is there another way to save the array while retaining the values connected to String keys?

Any assistance would be greatly appreciated!

javascript arrays

Answer 1

Answer №1

JavaScript does not have associative arrays. Instead, it uses objects where all keys are automatically converted to strings.

var newObj = {}; // <<< update made here

newObj["key1"] = "value1";
newObj[123] = "value2";

Answer 2

JavaScript does not have associative arrays. Instead, it uses objects where all keys are automatically converted to strings.

var newObj = {}; // <<< update made here

newObj["key1"] = "value1";
newObj[123] = "value2";

Answer 3

Answer №2

According to the comments from Daniel, the issue with your array lies not only in its persistence but also in its creation process.

This can be easily observed in your browser's console:

>var myArray = [];
<undefined
>myArray["key1"] = "value1";
<"value1"
>myArray
<[]

It is clear that trying to assign a value to an array using a String key does not function as expected.

Consider utilizing ES6 Maps or an object instead.

While Daniel has already provided the Object method, here is how you can use a Map:

var myMap = new Map();
myMap.set("key1", "value1");
myMap.set("123", "value2");

An advantage of using a Map is the simpler iteration process:

for (var [key, value] of myMap.entries()) {
  console.log(key + " = " + value);
}

Answer 4

According to the comments from Daniel, the issue with your array lies not only in its persistence but also in its creation process.

This can be easily observed in your browser's console:

>var myArray = [];
<undefined
>myArray["key1"] = "value1";
<"value1"
>myArray
<[]

It is clear that trying to assign a value to an array using a String key does not function as expected.

Consider utilizing ES6 Maps or an object instead.

While Daniel has already provided the Object method, here is how you can use a Map:

var myMap = new Map();
myMap.set("key1", "value1");
myMap.set("123", "value2");

An advantage of using a Map is the simpler iteration process:

for (var [key, value] of myMap.entries()) {
  console.log(key + " = " + value);
}

Storing Arrays with String Keys in LocalStorage using JavaScript

Answer №1

Answer №2

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