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sirdaiz
Asked: 2020-06-08 01:57:04 +0800 CST 2020-06-08 01:57:04 +0800 CST

Loop through a json optimally discarding duplicates

  • 772

Let's imagine I have this json

var personas = [
    {name: "paco", edad:23},
    {name: "pepe", edad:25},
    {name: "lucas", edad:30}
]

But really I have 1000 people and I want to get all the names of the people and that they are not repeated, I can do a forto go through all but I don't know if there is any other faster way to not go through 1000 objects

javascript

3 Answers

  1. Best Answer

    An easy and efficient way is to first sort the array, and remove the unique elements with just a for

    var personas = [
    {name: "paco", edad:23},
    {name: "paco", edad:23},
    {name: "pepe", edad:25},
    {name: "paco", edad:23},
    {name: "lucas", edad:30},
    {name: "paco", edad:23}
];

var names = personas.map(function (person) { return person.name; });
var sorted = names.sort();

var unique = sorted.filter(function (value, index) {
    return value !== sorted[index + 1];
});

console.log(unique);

    The last element is going to compare with undefined, which doesn't matter because they are going to be different

    This algorithm is O(N * logN)for sorting and O(N)removing duplicates, so it's pretty fast.

    • 7

  2. This could help you...

        var personas = [
        {name: "paco", edad:23},
        {name: "paco", edad:23},
        {name: "pepe", edad:25},
        {name: "paco", edad:23},
        {name: "lucas", edad:30},
        {name: "paco", edad:23},
        {name: "pepe", edad:25}
    ];

    var persona = {};
    var unicos = personas.filter(function (e) { 
        return persona[e.name] ? false : (persona[e.name] = true);
    });

    console.log(unicos);

    • 3

  3. You could make a custom filter to return what you need. Or even make one angular.forEachand store them in an array by contrasting them with a indexOf().

    • -2