Add an array to local storage and retrieve the array

Question

I am working with the local storage and I am struck in a problem.

I want to store the values for the key like this. The values are added dynamically and the should be separated by "," . I should retrieve them by comparing the value

here is my view

key                                       value
user1                                   a,b,c,d,e....

The values in the value field should be added dynamically. say I have fields username and add friend. the username should take the position key and add friend(dynamic) should take the value position.

first iteration:
username _a________
add friend _hello_______

localstorage : key                   value
                a                     hello
second iteration:

username _____a___
add friend : __stact___

local storage : key            value
                a              hello , stact
third iteration : 
username _____a___
add friend : __hi___

local storage : key            value
                a              hello , stact,hi

If i want to delete stact i have to write localStorage.removeKey(a[1]).

Please help me out as I am a newbie to this stuff I have used one of the answers below to my code but It didn't work. instead it is throwing error I have tried the following

var ls = (function () {
    var _key = function (username) {
        return username; 
    },
    _saveFriends = function (username, friends) {
        localStorage.setItem(ls._key(username), JSON.stringify(friends));
    };

    function getFriends(username) {
        return JSON.parse(localStorage.getItem(ls._key(username)) || '[]');
    }

    return {
        getFriends: getFriends,
        addFriend: function (username, friend) {
            var friends = getFriends(username);
            friends.push(friend);
            _saveFriends(friends);
        },
        removeFriend: function (username, friend) {
            var friends = getFriends(username);
            var index = friends.indexOf(friend);
            if (index >= 0) {
                friends.splice(index, 1);
            }
            _saveFriends(friends);
        }
    };
})();

function main()
{
ls.addFriend('revanth','aastha');
ls.addFriend('revanth','pobala');
ls.getFriends('revanth');

Here is the error Uncaught TypeError: undefined is not a function and the error is in this line return JSON.parse(localStorage.getItem(ls._key(username)));

I think you need to convert as JSON string when you save it otherwise convert as JSONify and work with them. — Naing Lin Aung, Mar 09 '15 at 04:36
possible duplicate of [Storing Objects in HTML5 localStorage](http://stackoverflow.com/questions/2010892/storing-objects-in-html5-localstorage) — A.J. Uppal, Mar 09 '15 at 04:42

score 0 · Answer 1 · answered Mar 09 '15 at 04:42

function addItem(user,str){
  // get value in localStorage and split into array
  var tempArr = localStorage.getItem(user).split(",");
  // if only adding unique items, check if unique
  // if (tempArr.indexOf(str)<0)...
  tempArr.push(str);
  // turn the temp array back into string
  var newStr = tempArr.join();
  // save back to localStorage
  localStorage.setItem(user, newStr);
}

score 0 · Accepted Answer · answered Mar 09 '15 at 04:47

Here is some functions you could use on the global namespace to make doing this easy in any framework:

var ls = (function () {
    var _key = function (username) {
        return username; // in case you want to namespace the keys later
    },
    _saveFriends = function (username, friends) {
        localStorage.setItem(ls._key(username), JSON.stringify(friends));
    };

    function getFriends(username) {
        return JSON.parse(localStorage.getItem(ls._key(username)) || '[]');
    }

    return {
        getFriends: getFriends,
        addFriend: function (username, friend) {
            var friends = getFriends(username);
            friends.push(friend);
            _saveFriends(friends);
        },
        removeFriend: function (username, friend) {
            var friends = getFriends(username);
            var index = friends.indexOf(friend);
            if (index >= 0) {
                friends.splice(index, 1);
            }
            _saveFriends(friends);
        }
    };
})();

// Use like so: 
//   ls.getFriends(username); 
//   ls.addFriend(username, friendname); 
//   ls.removeFriend(username, friendname);

Add an array to local storage and retrieve the array

2 Answers2