Answers for "match javascript arrays for same length and items"

check if array has same values javascript

const allEqual = arr => arr.every(v => v === arr[0]);
allEqual([1,1,1,1]);  // true

javascript get same elments from multiple arrays

var result = arrays.shift().filter(function(v) {
    return arrays.every(function(a) {
        return a.indexOf(v) !== -1;
    });
});