Javascript addition and subtraction with a string value

Question

I recently went through this typecast JS question:

Given '11'+10, the answer is 1110. It is clear that is not 21 because one is a string and JavaScript will treat both as string and perform concatenation instead of mathematical addition.

Why is '11'-10 is equal to 1, instead of something else?

Answer 1

Because the subtraction operator is not ambiguous and is only defined for numbers. Hence both operands are converted to numbers first.

See the specification:

• Addition
• Subtraction