function isUnique( arr, v, predicate, thisArg ) {
	var len;
	var i;

	len = arr.length;
	for ( i = 0; i < len; i++ ) {
		if ( !predicate.call( thisArg, arr[ i ], v ) ) {
			return false;
		}
	}
	return true;
}
Tests if a value is unique according to a predicate function when compared to a list of values.

@private
@param {Array} arr - input array
@param {*} v - test value
@param {Function} predicate - predicate function
@param {*} thisArg - evaluation context
@returns {boolean} boolean indicating whether a value is "unique"

@example
function predicate( a, b ) {
    return ( a !== b );
}

var bool = isUnique( [ 1, 2, 3 ], 1, predicate, null );
// returns false

bool = isUnique( [ 1, 2, 3 ], 4, predicate, null );
// returns true