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Angelos Chalaris
2022-11-05 16:04:35 +02:00
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blog_posts/js-proxy-array-negative-index.md
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@ -12,7 +12,7 @@ firstSeen: 2022-10-02T05:00:00-04:00
`Array.prototype.slice()` provides an easy way to access elements from the end of an array, using a negative `start` value. While this sounds convenient, the resulting value is an array, so it's necessary to use an index to get an individual element.
While this is usually not too bad, it's interesting to explore other options to understand the language better. In this case, we can use a `Proxy` object to allow accessing data in an array using negative indexes. To do so, an appropriate handler needs to be defined for the `get` trap.
This is usually not too bad, but it's interesting to explore other options to understand the language better. In this case, we can use a `Proxy` object to allow accessing data in an array using negative indexes. To do so, an appropriate handler needs to be defined for the `get` trap.
The trap's second argument corresponds to the passed index, however it's a string, so it must first be converted to a number using `Number()`. Then, `Array.prototype.length` can be used to calculate the position of the actual element. Finally, `Reflect.get()` can be used to get the value at the specific index, but expects its second argument to be a string.