compare two arrays and produceintersection, a diff b b diff a (compare is based on lengths/indexed, not sparse arrays)

array.indexDiff

var oldA = ['o1', 'o2', 'o3', 'o4'],
    newA = ['n0', 'n1', 'n2'];
//var oldA=['o1','o2'],newA=['n0','n1','n2'];

//var oldA=['o1','o2'],newA=['n0','n1'];
var changed = oldA.slice(0, Math.min(oldA.length, newA.length));
var added = newA.slice(oldA.length);
var deleted = oldA.slice(newA.length);

console.log(changed, added, deleted);



function array_indexDiff(a, b) {
    return {
        "a ∩ b": a.slice(0, Math.min(a.length, b.length)),
        // b not in a 
        "b \ a": b.slice(a.length),
        // a not in b
        "a \ b": a.slice(b.length)
    }
}

var d = array_indexDiff(oldA, newA);
console.log(d["a ∩ b"], d["b \ a"], d["a \ b"]);