I have a function in Javascript:
var a = [];
function SaveDataToLocalStorage(data)
{
var receiveddata = JSON.stringify(data);
a.push(receiveddata);
alert(a);
localStorage.setItem('session', a);
}
the data parameter is a JSON Object.
But everytime I click the button it overwrites the data in my localstorage.
Does anybody know how to do this?
There are a few steps you need to take to properly store this information in your localStorage. Before we get down to the code however, please note that localStorage (at the current time) cannot hold any data type except for strings. You will need to serialize the array for storage and then parse it back out to make modifications to it.
Step 1:
The First code snippet below should only be run if you are not already storing a serialized array in your localStorage session variable.
To ensure your localStorage is setup properly and storing an array, run the following code snippet first:
var a = [];
a.push(JSON.parse(localStorage.getItem('session')));
localStorage.setItem('session', JSON.stringify(a));
The above code should only be run once and only if you are not already storing an array in your localStorage session variable. If you are already doing this skip to step 2.
Step 2:
Modify your function like so:
function SaveDataToLocalStorage(data)
{
var a = [];
// Parse the serialized data back into an aray of objects
a = JSON.parse(localStorage.getItem('session')) || [];
// Push the new data (whether it be an object or anything else) onto the array
a.push(data);
// Alert the array value
alert(a); // Should be something like [Object array]
// Re-serialize the array back into a string and store it in localStorage
localStorage.setItem('session', JSON.stringify(a));
}
This should take care of the rest for you. When you parse it out, it will become an array of objects.
As of now, you can only store string values in localStorage. You'll need to serialize the array object and then store it in localStorage.
For example:
localStorage.setItem('session', a.join('|'));
or
localStorage.setItem('session', JSON.stringify(a));
One thing I can suggest you is to extend the storage object to handle objects and arrays.
LocalStorage can handle only strings so you can achieve that using these methods
Storage.prototype.setObj = function(key, obj) {
return this.setItem(key, JSON.stringify(obj))
}
Storage.prototype.getObj = function(key) {
return JSON.parse(this.getItem(key))
}
Using it every values will be converted to json string on set and parsed on get
let items = {
name: name,
size: size,
price: price
}
let itemsList = []
const getCarStorage = localStorage.getItem('productsList')
if(getCarStorage){
itemsList = JSON.parse(localStorage.getItem('productsList'))
itemsList.push(items)
localStorage.setItem('productsList', JSON.stringify(itemsList))
}else{
itemsList.push(items)
localStorage.setItem('productsList', JSON.stringify(itemsList))
}
Tengo un objeto llamado items que cambia en función de lo que reciba por parámetros. Una variable itemsList que es un array vacío.
Si no tengo nada en el localStorage, hago push del objeto dentro del array y lo seteo en el localStorage.
Si ya tengo el array creado en el localStorage, me lo guardo en itemsList, hago push de mi objeto items y vuelvo setearlo.
Así, si no tienes una matriz en localStorage, la creas, si la tienes haces push de lo nuevo.
var arr = [ 'a', 'b', 'c'];
arr.push('d'); // insert as last item
