greater than function does not work when 0 is inputted

Question

I need to validate the user input where user can only enter the value not equal to but greater than 0 and smaller than stated value. My validation logic works if i provide certain object

{required:true, greaterThan: 1, smallerThan: 50}

Here, if i input the value 0, then it displays an error message saying, value should be greater than 1 but if in case, i provide the following object instead

{required:true, greaterThan: 0, smallerThan: 50}

and I input the value 0 then it does not display an error message saying value should be greater than 0

Here is my validation logic

if (fieldValue.smallerThan && value && parseInt(value, 10) > fieldValue.smallerThan) {
    set(
        errors,
        key,
        `${fieldValue.label} should be smaller than ${fieldValue.smallerThan}`,
    )
    }
if (fieldValue.greaterThan && value && parseInt(value, 10) < fieldValue.greaterThan) {
    set(
        errors,
        key,
        `${fieldValue.label} should be greator than ${fieldValue.greaterThan}`,
    )
}

Answer 1

0 && any value

Will always result in false because 0 is considered as falsy value in javaScript

What You can do is

fieldValue.greaterThan >= 0 && ..

Answer 2

If you're just checking for existence of the greater than property in the fieldValue, which seems to be what you're doing, you might also considering editing your two checks to be:

if (fieldValue.smallerThan !== undefined && ...)

and

if (fieldValue.greaterThan !== undefined && ...)

In general, relying on the truthiness or falsiness of values gets you into trouble, and it's better to be explicit about what you are checking for.

Answer 3

always convert your inputs to an integer or float.

if(!(fieldValue.smallerThan < parseInt(value))){
  ...value must be smaller than 50
}

if(!(fieldValue.greaterThan > parseInt(value))){
  ...value must be greater than 0
}