Array that will only ever hold unique values

UniqArray

This package gives you a UniqArray class that does everything a regular Array does, except it will ignore it when you try to add any values that are already contained in it.

Frustratingly, there's a ton of packages in the index that provide just a single function to remove duplicates and return the array. All equivalents of let uniqueItems = [...new Set(items)]. This provides a convenient full-featured array where the duplicates never make it in, so you don't have to filter them out all the time.

Installation

npm install @ropg/uniqarray --save

Usage

const UniqArray = require('@ropg/uniqarray');

let a = new UniqArray(1,2,3,2);
console.log(a);                         // UniqArray(3) [ 1, 2, 3 ]
a.push(4,1,2,5,2);
console.log(a);                         // UniqArray(5) [ 1, 2, 3, 4, 5 ]
a.unshift(4,1,0);
console.log(a);                         // UniqArray(6) [ 0, 1, 2, 3, 4, 5 ]
console.log(a.concat([1,3,2,6,2,7]));   // UniqArray(8) [ 0, 1, 2, 3, 4, 5, 6, 7 ]

Limitations

Works for "scalar values" (such as numbers and strings), does not look inside objects (which includes arrays):

a = new UniqArray()
a.push (1,2,3,1,{a:true},{a:true},[1,2],[1,2])
console.log(a);
// UniqArray(7) [ 1, 2, 3, { a: true }, { a: true }, [ 1, 2 ], [ 1, 2 ] ]

( If you need something that will also reject objects with the same contents, you may want node-unique-array, although that doesn't have the same interface as a regular js array. )

Code

There really isn't all that much to it. Feel free to copy code below to your own project instead of depending on this module if you prefer that.

class UniqArray extends Array {
    constructor(...args) {
        return super(...new Set(args));
    }
    push(...args) {
        for (const a of args) if (!this.includes(a)) super.push(a);
        return this.length;
    }
    unshift(...args) {
        for (const a of args.reverse()) if (!this.includes(a)) super.unshift(a);
        return this.length;
    }
    concat(...args) {
        let r = new UniqArray(...this);
        for (const a of args) r.push(a);
        return r;
    }
}

module.exports = UniqArray