singleOrDefault

Tries to return the one and only element of the sequence.

JavaScript

// 1
Enumerable.create(1)
          .singleOrDefault();

// "TM"
Enumerable.create()
          .singleOrDefault('TM');

// "YS"
Enumerable.create(11)
          .singleOrDefault('x => typeof x === "string"',
                           'YS');

// "JS"
Enumerable.create(111, 222)
          .singleOrDefault('x => typeof x === "string"',
                           'JS');

// 2222
Enumerable.create(1111, 2222)
          .singleOrDefault('x => x > 1111',
                           'MK');

// THROWS EXCEPTION
Enumerable.create(11111, 22222, 33333)
          .singleOrDefault('x => x > 11111',
                           'PZ');