array2object

gistfile1.js

var arr = ['a','b','c','d','e'];
var objectify = function() {
    var o = {};
    arr.reduce( function (prev, cur, i, array) {
        (array.length % 2) && array.length - 1 === i ? o[cur] = null : 0;
        if(i % 2) {
            return o[prev] = cur;
        }
        else {
            return cur;
        }
    });
    return o;
}

var o = objectify(arr);
console.log(o);