i want the value from newUsername to be added to the localStorage setUsernamesArray, whereas in my code, it replaces the entire value.

Code

$('#signUpButton').click(function() {
  var newUsername = $('#usernameSignInBox').val();
  signedUpUsernames.push(newUsername);
  localStorage.setItem('setUsernamesArray', signedUpUsernames);
});

i want the value from newUsername to be added to the localStorage setUsernamesArray, whereas in my code, it replaces the entire value.

Code

$('#signUpButton').click(function() {
  var newUsername = $('#usernameSignInBox').val();
  signedUpUsernames.push(newUsername);
  localStorage.setItem('setUsernamesArray', signedUpUsernames);
});

• javascript
• jquery
• html
• css

Share Improve this question Follow edited Jun 20, 2020 at 9:12 CommunityBot 111 silver badge asked Mar 5, 2016 at 11:47 igetstuckalotigetstuckalot 23733 gold badges88 silver badges1616 bronze badges

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3 Answers 3

Sorted by: Reset to default 3

If you want to add to the array, you must realise that the value in localStorage isn't an array, it is a string. If you want that string to represent an array, and you want to update that array, you must do the following things:

• read the string, localStorage.getItem('setUsernamesArray'),
• then convert it to an array with JSON.parse,
• then push to the array,
• and then store it again with localStorage.setItem('setUsernamesArray', JSON.stringify(array))

localStorage always store values as a string, so stringify your array and store,

localStorage.setItem('setUsernamesArray', JSON.stringify(signedUpUsernames));

And before reading it just parse it,

var arrayFrmStorage = JSON.parse(localStorage.getItem("setUsernamesArray"))

localStorage.setItem will replace value of the key in localStorage.

Consider localStorage as a variable. when you do

var a = "Hello";
a = " World"

value of a is replaced. To avoid it, we use +=

var a = "Hello";
a += " World"

Similarly, you will have to create another object with updated value and write this to localStorage.

Following is an example.

function setValueToLS(key, prop, value){
  var _local = {};
  if(localStorage.getItem(key))
    _local = JSON.parse(localStorage.getItem(key));

  _local[prop] = value;

  localStorage.setItem(key, JSON.stringify(_local));
}