How to check duplicate elements in array?

No, there is no function via jQuery that does this. The closest thing to this reality would be .unique () , but only works with elements DOM .

But you can even develop your own method using .each and .inArray .

Take a look:

var times = ["Flamengo","Vasco","Corinthians","Fluminense","Corinthians","Fluminense","Palmeiras","Vasco"];
var timesNaoDuplicados = [];
$.each(times, function(i, elemento){
    if($.inArray(elemento, timesNaoDuplicados) === -1) timesNaoDuplicados.push(elemento);
});

//Se "printar" o timesNaoDuplicados: ["Flamengo", "Vasco", "Corinthians", "Fluminense", "Palmeiras"]

If you want to know only if an element is inside an array, use .inArray(elemento, Array) .

More about .inArray here .

In short, it returns you the position (index) where the element is inside the array. If it does not find anything, it returns -1.

With the magic of ES6 you can solve your problem with just one line of code. Ex:

var a = ["Ceará","Eusébio","Ceará"];
var b = ["JavaScript",">","All"];

function hasDuplicates(array) {
    return (new Set(array)).size !== array.length;
}

hasDuplicates(a);//true
hasDuplicates(b);//false