
How to remove duplicate elements in JavaScript ?
tl;dr
[Update on 2 Dec 2019]
Ways to remove duplicated elements in JavaScript
- Array.prototype.filter()
- JSON
- Set
#1 Using Array.prototype.filter()
const duplicated = [
"John",
"Johnny",
"Jonathan",
"Christine",
"Conan",
"Christine",
"Johnny"
];
duplicated.filter(
(element, index) => duplicated.indexOf(element) === index
)
// Expected result
// [ 'John', 'Johnny', 'Jonathan', 'Christine', 'Conan' ]
#2 JSON
const duplicated = [
"John",
"Johnny",
"Jonathan",
"Christine",
"Conan",
"Christine",
"Johnny"
];
const unique = {};
duplicated.forEach(val => {
unique[val] = val;
});
console.log(Object.values(unique));
// or console.log(Object.keys(unique))
// Expected result
// [ 'John', 'Johnny', 'Jonathan', 'Christine', 'Conan' ]
#3 Set
const duplicated = [
"John",
"Johnny",
"Jonathan",
"Christine",
"Conan",
"Christine",
"Johnny"
];
// first, how to convert Array to Set
const setFromArray = new Set([]);
// second, how to convert Set back to Array
const arrayFromSet = [...new Set([])];
// So, in order to remove duplicate elements using Set
// first, convert the Array to Set
// Then, convert back to Array
console.log([...new Set(duplicated)]
Comments
(2 Comments)
Bookmarked!, I love your blog!
Thank you.
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