javascriptdata-structuresintersection

Simplest code for array intersection in javascript

What's the simplest, library-free code for implementing array intersections in javascript? I want to write

intersection([1,2,3], [2,3,4,5])

and get

[2, 3]
Solution

  • Use a combination of Array.prototype.filter and Array.prototype.includes:

    const filteredArray = array1.filter(value => array2.includes(value));

    For older browsers, with Array.prototype.indexOf and without an arrow function:

    var filteredArray = array1.filter(function(n) {
    return array2.indexOf(n) !== -1;
});

    NB! Both .includes and .indexOf internally compares elements in the array by using ===, so if the array contains objects it will only compare object references (not their content). If you want to specify your own comparison logic, use Array.prototype.some instead.