Remove duplicates in an object array Javascript

Question

I have an array of objects

list = [{x:1,y:2}, {x:3,y:4}, {x:5,y:6}, {x:1,y:2}]

And I\'m looking for an efficient way (if possible O(

Answer 1

Plain javascript (ES2015), using Set

const list = [{ x: 1, y: 2 }, { x: 3, y: 4 }, { x: 5, y: 6 }, { x: 1, y: 2 }];

const uniq = new Set(list.map(e => JSON.stringify(e)));

const res = Array.from(uniq).map(e => JSON.parse(e));

document.write(JSON.stringify(res));

Answer 2

Try using the following:

list = list.filter((elem, index, self) => self.findIndex(
    (t) => {return (t.x === elem.x && t.y === elem.y)}) === index)

Answer 3

One liners for ES6+

If you want to find uniq by x and y:

arr.filter((v,i,a)=>a.findIndex(t=>(t.x === v.x && t.y===v.y))===i)

If you want to find uniques by all properties:

arr.filter((v,i,a)=>a.findIndex(t=>(JSON.stringify(t) === JSON.stringify(v)))===i)

Answer 4

The following will work:

var a = [{x:1,y:2}, {x:3,y:4}, {x:5,y:6}, {x:1,y:2}];

var b = _.uniq(a, function(v) { 
    return v.x && v.y;
})

console.log(b);  // [ { x: 1, y: 2 }, { x: 3, y: 4 }, { x: 5, y: 6 } ]

Answer 5

Using lodash you can use this one-liner:

 _.uniqBy(list, e => { return e.x && e.y })

Answer 6

Filter the array after checking if already in a temorary object in O(n).

var list = [{ x: 1, y: 2 }, { x: 3, y: 4 }, { x: 5, y: 6 }, { x: 1, y: 2 }],
    filtered = function (array) {
        var o = {};
        return array.filter(function (a) {
            var k = a.x + '|' + a.y;
            if (!o[k]) {
                o[k] = true;
                return true;
            }
        });
    }(list);

document.write('<pre>' + JSON.stringify(filtered, 0, 4) + '</pre>');