how to set value to some desired index of array in javascript?

Question

I have saving cart items in localStorage of javascript. I use product_id for index of array in javascript, this array contain of object with some property.

let cart = JSON.parse(localStorage.getItem('cart'));
cart[cartObject.product_id] = {
    quantity : cartObject.product_quantity,
    price : cartObject.product_price,
    holding : cartObject.product_holding
}
localStorage.setItem('cart' , JSON.stringify(cart));

the problem is for example when my product_id is 8, localStorage is :

0: null

1: null

2: null

4: null

5: null

6: null

7: null

8: {quantity: 15, price: 16000, holding: 44}

what about 4000 ? is localStorage goes overflow ?

this problem does not exist in php, I want to access directly to specific index of array. for example get cart[4432].price.

how to do that ?

thanks in advance

What did you try? Nothing prevents you to do card[4432] in JavaScript. Array can accept any index, but for performance reasons is advised to use objects if the indices are sparse — Christian Vincenzo Traina
– Christian Vincenzo Traina, Commented Sep 3, 2022 at 10:27

Saif Ali Khan · Accepted Answer · 2022-09-03 10:41:48Z

1

I think you need to change the way you store the products. Instead of using an Array, you can use an Object.

// Suppose localStorage.getItem('cart') contains an {} instead of []

let cart = JSON.parse(localStorage.getItem('cart')); // Should return {}

cart[cartObject.product_id] = {
    quantity : cartObject.product_quantity,
    price : cartObject.product_price,
    holding : cartObject.product_holding
}

localStorage.setItem('cart' , JSON.stringify(cart)); // Should save {"product_id": {"quantity": 1, "price": 100, "holding": "product_holder"}}

// If you want to loop like an Array, you would do the following:
Object.values(cart).forEach(function(product) {
  // Do something with your product...
})

answered Sep 3, 2022 at 10:41

Saif Ali Khan

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Comments

Gregor · Accepted Answer · 2022-09-03 10:31:11Z

1

I guess the problem is that you use arrays for your task. A better way would be to use maps:

let cart = new Map( JSON.parse( localStorage.getItem('cart') ) );

cart.set( cartObject.product_id, {
  quantity : cartObject.product_quantity,
  price : cartObject.product_price,
  holding : cartObject.product_holding,
});

localStorage.setItem( 'cart', Array.from( cart ) );

answered Sep 3, 2022 at 10:31

Gregor

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2 Comments

aref razavi Over a year ago

Now can I access to cart[4432].quantity ?

Gregor Over a year ago

@arefrazavi You can access it via cart.get( 4432 ).quantity (see developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… for reference)

Ankit · Accepted Answer · 2022-09-03 10:29:47Z

0

Try to fix your code like this:

var colors=["red","blue"];
var index=1;

//insert "white" at index 1
colors.splice(index, 0, "white");   //colors =  ["red", "white", "blue"]

answered Sep 3, 2022 at 10:29

Ankit

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