Things I want to do
This explains how to implement Unique (removing duplicates from an array) in JavaScript.
I will introduce two methods using filter and set.
implementation
The man used the implementation
The Filter function is used to remove duplicate elements.
The `findIndex()` method searches for an element identical to the one being checked, and if an element with a smaller index is found, it is selected for deletion. (`arr.findIndex((ele) => element == ele) == index)`
(You might be wondering why the element with the larger index isn’t deleted, but it’s not a problem because it’s deleted when the element with the larger index is checked. In the example below, the first ‘element0’ is not deleted, but the second ‘element0’ is.)
const elements = ["element0", "element0", "element1", "element2", "element3", "element4","element1","element1","element2"];
const result = elements.filter((element, index, arr) =>
arr.findIndex((ele) => element == ele) == index
);
console.log(result);Result：
Array ["element0", "element1", "element2", "element3", "element4"]application
Whether elements are identical is determined by the function to which findIndex is also passed, so they don’t actually need to be the same in the true sense.
The example below shows the results of running Unique(result), which is case-sensitive, and Unique(result), which is case-insensitive.
const elements = ["Element0", "element0", "element1", "element2", "element3", "element4","element1","Element1","element2"];
const result = elements.filter((element, index, arr) =>
arr.findIndex((ele) => element == ele) == index
);
const result2 = elements.filter((element, index, arr) =>
arr.findIndex((ele) => element.toUpperCase() == ele.toUpperCase()) == index
);
console.log(result);
console.log(result2);Result：
Array ["Element0", "element0", "element1", "element2", "element3", "element4", "Element1"]
Array ["Element0", "element1", "element2", "element3", "element4"]Additionally, if you want to check for uniqueness in an array of objects, you can do so using a check like `element.name == ele.name`.
Implementation using Set
Create a Set (similar to an Array, but without duplicate elements) and convert it to an Array.
const elements = ["element0", "element0", "element1", "element2", "element3", "element4","element1","element1","element2"];
console.log([...new Set(elements)]);Result：
Array ["element0", "element1", "element2", "element3", "element4"]When implementing Unique using Set, it’s common to convert to an Array using from(), but it’s cleaner to use spread(…) for the conversion.
Result
I was able to implement Unique (removing duplicates from an array) in JavaScript.
Websites I used as references
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