Probably a rookie question, but how do I prevent the decrement from going past zero into the negative numbers?

public counter : number = 0;
increment(){
  this.counter += 1;
}

decrement(){
  this.counter -= 1;
}

Probably a rookie question, but how do I prevent the decrement from going past zero into the negative numbers?

public counter : number = 0;
increment(){
  this.counter += 1;
}

decrement(){
  this.counter -= 1;
}

• javascript

• 2 developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… – Quentin Commented Feb 23, 2020 at 19:55
• Is this TypeScript? – tadman Commented Feb 23, 2020 at 19:56
• there is no way to prevent decrement (--) or subtraction assignment (-=) from going below 0. Apply logic to determine whether or not you need to modify the value in first place – Max Commented Feb 23, 2020 at 20:19

4 Answers 4

For clarity, I suggest to use the Math.max() function to make sure that the value is always greater than or equal to 0.

decrement(){
  this.counter = Math.max(0, this.counter - 1);
}

This is not the fastest way to do this but as long as you don't call decrement() in a loop for several hundred thousand times, the performance degradation is too small to be perceived.

You simply check if the counter is still greater than zero and only if so you actually decrement your counter

decrement(){
  if(this.counter > 0){
    this.counter -= 1
  }
}

Write the function to clamp it at zero:

decrement(){
  this.counter -= 1;
  if (this.counter < 0) {
     this.counter = 0;
  end
}

you can do it using ternary operator too.

value > 0 ? value - 1 : 0