Check if Number is not Greater than 0 in JavaScript

# Check if a Number is not Greater than 0 in JavaScript

Use the less than or equals to <= operator to check if a number is not greater than zero, e.g. if (num <= 0) {}.

The comparison will return true if the number is not greater than zero and false otherwise.

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const num = -5;

if (num <= 0) {
  // 👇️ this runs
  console.log('✅ number is not greater than 0');
} else {
  console.log('⛔️ number is greater than 0');
}

The less than or equals to <= operator returns true if the value to the left is less than or equal to the value to the right.

If the number is less than or equal to 0, then it's not greater than 0.

If you have to check if a number is not greater than 0 often, define a reusable function.

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function isNotGreaterThanZero(num) {
  return num <= 0;
}

console.log(isNotGreaterThanZero(0)); // 👉️ true
console.log(isNotGreaterThanZero(5)); // 👉️ false
console.log(isNotGreaterThanZero(-10)); // 👉️ true

if (isNotGreaterThanZero(-5)) {
  // 👇 this runs
  console.log('The number is not greater than zero');
} else {
  console.log('The number is greater than zero');
}

The isNotGreaterThanZero function takes a number as a parameter and returns true if the number is not greater than zero and false otherwise.

# Check if a Number is not Greater than 0 using logical NOT (!) operator

Alternatively, you can use the logical NOT (!) operator.

If the number is not greater than 0, the expression returns true, otherwise false is returned.

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const num = -5;

if (!(num > 0)) {
  // 👇️ this runs
  console.log('✅ number is not greater than 0');
} else {
  console.log('⛔️ number is greater than 0');
}

We used the logical NOT (!) operator to negate the greater than sign.

Note that we had to wrap the condition in parentheses.

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const num = -5;

// ⛔️ BAD (don't do this)
console.log(!num > 0); // 👉️ false

The code sample above doesn't use parentheses, so we convert the num variable to a boolean and negate it.

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const num = -5;

console.log(!num); // 👉️ false

All numbers other than 0 are truthy values, so when converted to a boolean, they get converted to true and when negated, they become false.

Instead, we want to wrap the expression in parentheses.

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const num = -5;

if (!(num > 0)) {
  console.log('✅ number is not greater than 0');
} else {
  console.log('⛔️ number is greater than 0');
}

Now we first check if the number is greater than 0, then convert the result to a boolean and negate it.

If the number is greater than 0, the expression returns true and when the logical NOT (!) operator is applied, false is returned, so the else block runs.

The if block runs only if the number is not greater than 0.

If you have to do this often, define a reusable function.

Copied!
const num = -5;

function isNotGreaterThanZero(num) {
  return !(num > 0);
}

console.log(isNotGreaterThanZero(0)); // 👉️ true
console.log(isNotGreaterThanZero(5)); // 👉️ false
console.log(isNotGreaterThanZero(-10)); // 👉️ true

if (isNotGreaterThanZero(-5)) {
  // 👇 this runs
  console.log('The number is not greater than zero');
} else {
  console.log('The number is greater than zero');
}

The function takes a number as a parameter and returns true if the number is not greater than 0 and false otherwise.

Which approach you pick is a matter of personal preference. I'd use the if (num <= 0) {} comparison as I find it more readable and intuitive.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Check if a Number is Between Two Numbers in JavaScript
• Check if one Number is Multiple of another in JavaScript
• Check if a String contains Numbers in JavaScript
• Check if String contains only Letters and Numbers in JS
• How to Check if a Value is a Number in JavaScript