How to use regular expression for calculator input with javascript?

Question

I am trying to write simple calculator with JavaScript. I want to check if user input is correct or not. I wrote regular expression in order to make sure user input is prope

Answer 1

^[-+]?

Is correct, but then

[0-9]{0,}

Is not, you want + quantifier as if you use {0,} (which is the same as *) you could have "+*9" being correct. Then,

([-+*/]?)[0-9]+

Is wrong, you want :

([-+*/]+[-+]?[0-9]+)*

So you will have for instance *-523+4234/-34 (you can use an operand on an either negative or positive number, or not precised number which would mean obviously positive)

So finally, you would have something like :

^[-+]?[0-9]+([-+*/]+[-+]?[0-9]+)*$

Of course, you can replace class [0-9] with \d