Popular posts

You have to think of the localStorage field as an array with potential data from the beginning.

1. Check if the field exists. If not, create it with an empty array
2. Store the value into a variable
3. Do the data manipulation (for example: append the new item)
4. Store the new array back to the localStorage field

In code:

// 1. and 2. where `items` is always an array of item-objects with 0..n elements
const items = (() => {
  const fieldValue = localStorage.getItem('cart');
  return fieldValue === null
    ? []
    : JSON.parse(fieldValue);
})();

// 3.
items.push({"name":"T-Shirt","price":3.99,"quantity":1});

// 4.
localStorage.setItem('cart', JSON.stringify(items));

Or with storejs:

// 1. and 2. where `items` is always an array of item-objects with 0..n elements
const items = store.get('cart') || [];

// 3.
items.push({"name":"T-Shirt","price":3.99,"quantity":1});

// 4.
store.set('cart', items);