Input number with "+" and pointer : I have this simple input:

    <input type="number" step="0.01">
This all inputs make success outputs:<br>
a) 2.00<br>
b) 2,00<br>
c) +2,00<br>

But input "+2.00" fail.
I want to know why it happens. 
Js recognize "+2.00" as a number.