JSFiddle - React, Tailwind, and code Playground

by dzul1983

JavaScript

function getArrayItemOccurrence(arr) {
    var a = [], b = [], prev;
    
    arr.sort();
    for ( var i = 0; i < arr.length; i++ ) {
        if ( arr[i] !== prev ) {
            a.push(arr[i]);
            b.push(1);
        } else {
            b[b.length-1]++;
        }
        prev = arr[i];
    }
    
    return [a, b];
}

var str = [];
str[0] = ['a', 'b', 'c', 'e'];
str[1] = ['d', 'e', 'b', 'a'];
str[2] = ['a', 'e'];

var fullstr = [];
fullstr = fullstr.concat(str[0], str[1], str[2]);

var result = getArrayItemOccurrence(fullstr);

var occursInAll = [];
for(var i=0;i<result[1].length;i++){
    if(result[1][i] == str.length){
        occursInAll.push(result[0][i]);
    }
}

document.write(occursInAll.join(', ') + ' occurs in all arrays')