Replace or push to array in javascript

Question

I have an array of orders and when i recieve a message from my websocket with a new placement order or a modified order i want to check against my orders array, if there is an exisitng order with the websocket message replace the object in the array with the websocket message, else push it to the array.

example:

const orderArr = [
{
id: 1,
item: 'apple',
price: 20
},
{
id: 2,
item: 'mango',
price: 10
},
{
id: 3,
item: 'cucumber',
price: 300
}
]

const webSocketOrder = {
id: 1,
item: 'apple',
price: 40
}

// what should happen to the order array
[
{
id: 1,
item: 'apple',
price: 40
},
{
id: 2,
item: 'mango',
price: 10
},
{
id: 3,
item: 'cucumber',
price: 300
}
]

but if the webSocketOrder is a new item with a new id it should be added as a new item in the orderArr

what i have done

const foundOrder = orderArr.find(
          (x) => x.id === webSocketOrder.id
        );
        if (foundOrder) {
          orderArr.map((ord) =>
            ord.id === webSocketOrder.id 
              ? webSocketOrder
              : ord
          );
        } else {
          orderArr.unshift(webSocketOrder);
        }

this doesnt work for some reason, please can someone help?

Read about array operations in detail. Your find, map and unshift usage is wrong — Beshambher Chaukhwan
– Beshambher Chaukhwan, Commented May 26, 2021 at 12:23
Why are you calling array like a function: orderArr( (x) => ..) — adiga
– adiga, Commented May 26, 2021 at 12:24

Sunny · Accepted Answer · 2021-05-26 12:44:24Z

3

You can use find()/findIndex() to loop over the array just once.

 const index = orderArr.findIndex((obj) => obj.id === webSocketOrder.id);

    if (index === -1) {
        orderArr.push(webSocketOrder);
    } else {
        orderArr[index] = webSocketOrder;
    }

edited May 26, 2021 at 12:44

answered May 26, 2021 at 12:33

Sunny

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1 Comment

Jose Mhlanga Over a year ago

Great stuff. Saved my day!

james · Accepted Answer · 2023-04-24 14:57:17Z

0

If you're replacing the order in place (not treating the array as immutable) you can use splice

const index = orderArr.findIndex((obj) => obj.id === webSocketOrder.id);

orderArr.splice(index > -1 ? index : orderArr.length, index > -1 ? 1 : 0, webSocketOrder);

answered Apr 24, 2023 at 14:57

james

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