Edit in JSFiddle

!Array.prototype.every && (Array.prototype.every = function (callback) {

    callback = callback || function () { return false; };

    var a = this;

    for (var n in a) {
        if (!callback.call(this, a[n], n, a)) {
            return false;
            break;
        }
    }

    return true;
});

!Array.prototype.some && (Array.prototype.some = function (callback) {

    callback = callback || function () { return false; };

    var a = this;
    var ret = false;

    for (var n in a) {
        if (callback.call(this, a[n], n, a)) {
            return true;
            break;
        }
    }

    return false;
});

var a = [4, 5, 6];
console.log(a.every(function (e, i, arr) { return arr[i] === 4; }));
console.log(a.every(function (e, i, arr) { return arr[i] === 4 || arr[i] === 5 || arr[i] === 6; }));

var b = [4, 5, 6];
console.log(b.some(function (e, i, arr) { return arr[i] === 4; }));
console.log(b.some(function (e, i, arr) { return arr[i] === 7; }));