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JavaScript function return boolean | Example code

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You can return a boolean value from a JavaScript function. Create a function and use the if statement to evaluate the given value to the function. And return true or false according to the conditions.

function  func(){
  return true;
}
isBool = func();
console.log(typeof (isBool));   // output - string

let isBool = func();
console.log(typeof (isBool));   // output - boolean

for conditions statement

if (expression) {
  return true;
}
else {
  return false;
}

JavaScript function returns a boolean

Simple example code passing the newly defined quarter variable a function with a parameter of ‘n’ that I then divide by 4 to see if it returns 1 for true, or 0 (else) for false.

<!DOCTYPE html>
<html>
<body>
  <script>
    var quarter = function(n) {
      if (n % 4 == 0){
        return true;
      } else {
        return false;
      }
    };

    console.log(quarter(4))
    console.log(quarter(1))

  </script>
</body>
</html>

Output:

JavaScript function return boolean

Return a boolean true or false in a JavaScript function

A function that checks if a person is old enough to vote by checking their age. This function is called isOldEnoughToVote(age) and takes an argument age. It checks if the age is greater than or equal to 18. If returns true or false based on that comparison.

function isOldEnoughToVote(age) {
  return age >= 18;
} 

console.log(isOldEnoughToVote(17)); // false
console.log(isOldEnoughToVote(18)); // true

Or, if you like more Arrow functions

const isOldEnoughToVote = (age) => age >= 18;

// The first => is an arrow function's "Fat Arrow"
// The second >= is an greater-or-equal operator

console.log(isOldEnoughToVote(17)); // false
console.log(isOldEnoughToVote(18)); // true

If you need to return two strings "true" and "false" you can do it like:

function isOldEnoughToVote(age) {
  if (age < 18) {
    return "false";
  } else {
    return "true";
  }
} 

console.log(isOldEnoughToVote(17)); // "false"
console.log(isOldEnoughToVote(18)); // "true"

Or by using an Arrow Function and the Ternary operator ?:

const isOldEnoughToVote = (age) => age < 18 ? "false" : "true";

console.log(isOldEnoughToVote(17)); // "false"
console.log(isOldEnoughToVote(18)); // "true"

Source: stackoverflow.com

Comment if you have any doubts or suggestions on this JS function topic.

Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.

OS: Windows 10

Code: HTML 5 Version

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