Returns a value as predicate.

A predicate has the following structure:

function (x) : boolean;

Examples

// returns (true)
var predicate1 = Enumerable.toPredicateSafe();

// from Lambda
var predicate2 = Enumerable.toPredicateSafe('x => x != 2');

// from function
var predicate3 = Enumerable.toPredicateSafe(function(x) {
    return x != 2;
});

// THROWS EXCEPTION
Enumerable.toPredicateSafe('test');