How to prevent multiple operands in javascript calculator?

Question

Eg: 2++2, when i press "+" more than one time consecutively it should not add another plus sign. below is my code of calculator

https://code.sololearn.com/WZMx7gAFYd1M/?ref=app

Answer 1

if (!input.endsWith(op)) {
input += op
}
//like that...