Single

Description:

This method returns single item. When you expect sequence contains one item . If sequence has more than one element or is empty the method throws an exception.

Sample:

let items = ['One', 'Two', 'Three', 'Four', 'Five', 'Six', 'Seven', 'Eight', 'Nine', 'Ten'];

let singleList = ['one'];

let single = singleList.asEnumerable().single();

console.log(single);

try {
  single = empty.asEnumerable().single();
}
catch (err) {
  console.error(err.message);
}

single = items.asEnumerable().single(item => item.indexOf('O') === 0);

try {
  single = items.asEnumerable().single(item => item.indexOf('F') === 0);
}
catch (err) {
  console.error(err.message);
}