Try to save object like this:
var testObject = { 'one': 1, 'two': 2, 'three': 3 }; // Put the object into storage localStorage.setItem('testObject', JSON.stringify(testObject)); // Retrieve the object from storage var retrievedObject = localStorage.getItem('testObject'); console.log('retrievedObject: ', JSON.parse(retrievedObject));


And in your code we can do it like this

$('#btnLogin').click(function () { $.ajax({ url: '/token', method: 'POST', contentType: 'application/json', data: { userName: $('#txtFullname').val(), password: $('#txtPassword').val(), grant_type: 'password' }, // Khi đăng nhập thành công, lưu token vào sessionStorage success: function (response) { var obj= { 'accessToken': response.access_token}; localStorage.setItem(JSON.stringify(obj)); window.location.href = "User.html"; }, // Display errors if any in the Bootstrap alert <div> error: function (jqXHR) { $('#divErrorText').text(jqXHR.responseText); $('#divError').show('fade'); } }); });

Looking at the [Apple][1], [Mozilla][2] and [Mozilla again][3] documentation, the functionality seems to be limited to handle only string key/value pairs.
A workaround can be to [*stringify*][4] your object before storing it, and later parse it when you retrieve it:

var testObject = { 'one': 1, 'two': 2, 'three': 3 }; // Put the object into storage localStorage.setItem('testObject', JSON.stringify(testObject)); // Retrieve the object from storage var retrievedObject = localStorage.getItem('testObject'); console.log('retrievedObject: ', JSON.parse(retrievedObject));

[1]: https://developer.apple.com/library/archive/documentation/iPhone/Conceptual/SafariJSDatabaseGuide/Name-ValueStorage/Name-ValueStorage.html [2]: https://developer.mozilla.org/en-US/docs/Web/API/Web_Storage_API [3]: https://developer.mozilla.org/en-US/docs/Web/API/Storage/setItem [4]: https://www.w3schools.com/js/js_json_stringify.asp