Javascript array Prototype find

Question

on developer.mozilla i found an example of working with array find:

const inventory = [
  {name: 'apples', quantity: 2},
  {name: 'bananas', quantity: 0},
  {name: 'cherries', quantity: 5}
];

function isCherries(fruit) {
  return fruit.name === 'cherries';
}

console.log(inventory.find(isCherries));
// { name: 'cherries', quantity: 5 }

I have an cart Class with an array of objects, so, i am having a function checkQuantity which should return whatever item satisfies the condition. Also i am having same function where i need to find.

i tried to implement this approach from mozilla, and i did like this:

itemSearch(item) {
        return item.id === this.id &&
            item.color === this.color &&
            item.size === this.size
    } // method which i need

and i am using it like this:

 checkQuantity() {
        return this._cart.find(this.itemSearch()).quantity < this.stockCount();
    }

Where i obtain undefined, however i know for sure it must find , because if i use .find(element => conditions) instead of that method, it works.

so, my Question is why it does not work? Sorry for bad english.

Take another look at the example you got inspiration from. They do .find(isCherries), not .find(isCherries()) — blex
– blex, Commented Apr 10, 2021 at 11:56
@blex, my first try was without () , it does not work anyway. — iftwMZ
– iftwMZ, Commented Apr 10, 2021 at 11:57
@iftwMZ, you have to bind to this explicitly: this._cart.find(this.itemSearch.bind(this)). Otherwise you lose the correct context and this will point to window instead. — Đinh Carabus
– Đinh Carabus, Commented Apr 10, 2021 at 11:58

Nina Scholz · Accepted Answer · 2021-04-10 11:58:26Z

1

By using this, you need to specify this as well for Array#find, beside not to use the result of the call of the function.

checkQuantity() {
    return this._cart.find(this.itemSearch, this).quantity < this.stockCount();
}

answered Apr 10, 2021 at 11:58

Nina Scholz

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1 Comment

iftwMZ Over a year ago

Works. thank you so much. Waiting 10 minutes and i mark as answered!

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