Angular2 / JavaScript - 如何显示所有localStorage保存的变量并获取所有键的总长度？

Question

I am working on an Angular2 app, in which I need to store items that were added by the user to the shopping cart. For that, I am using local storage to save the items temporarily. Each category (ex. shoes, clothes....) is saved in the local storage as a key; its value is an array that contains all the added items and belongs to the same category key .

I have multiple keys, each of them has a value which is an array. I want to access to the stored keys and also get the length of value of all keys

Ex: key 1 has a value that has a length of 5. Key 2 has a value that has a length of 12.

So the total length is 12+5=17

Any idea on how to achieve that?

Answer 1

Why not just store it all on an object and JSON.stringify it to save, JSON.parse to load (Angular2 may have a better method of accessing localstorage).

var store = {
   "categories" : {
       "shoes" : ['key1', 'key2'],
       "clothes" : []
    }

}

function getCategoryLength(cat){
    var total = 0;
    for(var i = 0; i < store.categories[cat].length){
       total += store.categories[cat][i].length;
    }
    return total
}
getCategoryLength("shoes")

Answer 2

you can access keys with Object.keys like below

var storedKeys = Object.keys(localStorage);
//length = storedKeys.length 



/*
//Assuming your have store structure like below
  localStorage = {
                    key1: [1, 2, 3],
                    key2: [1, 2, 3, 4, 5],
                    key3: "text"
                 };
*/

var flattenKeysLength = 0;
for(var key in localStorage) 
    flattenKeysLength += 
        (typeof localStorage[key] == "string")? 1:localStorage[key].length;