chrome中的本地存储

Question

i need help!

I am looking to uses chrome local storage in one of my apps. Basically this is supposed to be a shopping list app that store locally previously entered items as an object in JavaScript.

i must be doing something wrong because when there is nothing in local storage and i add an item i gets saved fine but then whenever i add a second item, the previous item gets replaced.

Here's my code so far

function useLocalStorage(shoppingListItem){

    let shoppingApp = {};
    
    if (localStorage.getItem(shoppingApp) === null){
       shoppingApp.shoppingList = [];
    }
    else {
       shoppingApp.shoppingList = JSON.parse(localStorage.getItem('shoppingApp.shoppingList'));
    }

    shoppingApp.shoppingList.push({
      shoppingListItem : shoppingListItem,
      checked : false,
    });

    localStorage.setItem(shoppingApp.shoppingList.shoppingListItem, 
                         JSON.stringify(shoppingApp.shoppingList));
}

Answer 1

Did you see how your localStorage looks like after executing the function?

If you did not do typos in code:

localStorage.setItem(
    shoppingApp.shoppingList.shoppingListItem, 
    JSON.stringify(shoppingApp.shoppingList)
);

The first argument will return undefined , you are trying to access proprty of shoppingListItem on shoppingList which is array. To get any value you need to access the item directly with for example shoppingApp.shoppingList[0] . Because of this error(?) for me it saves the list in undefined key.

let shoppingApp = {};

if (localStorage.getItem(shoppingApp) === null){
    shoppingApp.shoppingList = [];
}

This if statement is always true . What you are doing is trying to access item with key {} and because there is no key like that in your localStorage it returns null so your new shopping list is empty. You probably wanted to use here string: if (localStorage.getItem('shoppingApp') === null) . If you were to write the {} as a key so you could access it later - it would get parsed and the key would be "[object Object]" so I do not think that is your intended behaviour.