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ECMAScript proposal for Deduplicating method of Array.

Deduplication is one of the most common requirements in Data processing, especially in large Web Apps nowadays.

In Lodash,*uniq* methods are alsovery popular:

But[...new Set(array)] in ECMAScript 6 isn't enough forNon-primitive values, and now, we may need aArray.prototype.uniqueBy().

WhileArray.prototype.uniqueBy() invoked with:

1. no parameter, it'll work as[...new Set(array)];

2. oneindex-key parameter (Number,String orSymbol), it'll get values from each array element with the key, and then deduplicates the origin array based on thesevalues;

3. onefunction parameter, it'll call this function for each array element, and then deduplicates the origin array based on thesereturned values.

Notice:

• theReturned value is a new array, no mutation happens in the original array
• Empty/nullish items are treated as nullish values
• 0 &-0 are treated as the same
• AllNaNs are treated as the same

[1,2,3,3,2,1].uniqueBy();// [1, 2, 3]constdata=[{id:1,uid:10000},{id:2,uid:10000},{id:3,uid:10001}];data.uniqueBy('uid');// [//     { id: 1, uid: 10000 },//     { id: 3, uid: 10001 }// ]data.uniqueBy(({ id, uid})=>`${id}-${uid}`);// [//     { id: 1, uid: 10000 },//     { id: 2, uid: 10000 },//     { id: 3, uid: 10001 }// ]

A polyfill is available in thecore-js library. You can find it in theECMAScript proposals section.

A simple polyfill from the proposal repo write in TypeScript.

• Author:@TechQuery
• Champion:@Jack-Works