What is the best way to set a value to null in JavaScript?

Question

What is the best way to set a value to null in JavaScript?

Seeking assistance with the "Days Of The Week Exercise" in JavaScript. I have searched MDN and made numerous attempts, but I am still unsure about what null represents and how to effectively use it.

If the argument (num) is less than 1 or greater than 7, the function is expected to return null.

const days = ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday','Sunday'];

let returnDay = (num) => {
    if (num >= 1 && num <= 7) {
        return days[num - 1];
    } else {
        return null;
    }
};

returnDay(1); // Monday
returnDay(7); // Sunday
returnDay(4); // Thursday
returnDay(0); // null

javascript arrays arguments

Answer 1

Answer №1

1 <= num <= 7 may not function as you expect in JavaScript. This is because binary operators are evaluated from left to right. Therefore, 1 <= num <= 7 actually translates to (1 <= num) <= 7, resulting in either true <= 7 or false <= 7, depending on the value of num. Despite this, it will always return true, although comparing booleans with numbers is not recommended. As the condition always evaluates to true, the else section is never reached, thus null is never returned.

To achieve the desired outcome, consider using the following structure:

if (1 <= num && num <= 7) {
   ...
} else {
   ...
}

Additionally, keep in mind that array indices commence at 0. In the provided example, days[1] would yield 'Tuesday', not 'Monday'.

Answer 2

1 <= num <= 7 may not function as you expect in JavaScript. This is because binary operators are evaluated from left to right. Therefore, 1 <= num <= 7 actually translates to (1 <= num) <= 7, resulting in either true <= 7 or false <= 7, depending on the value of num. Despite this, it will always return true, although comparing booleans with numbers is not recommended. As the condition always evaluates to true, the else section is never reached, thus null is never returned.

To achieve the desired outcome, consider using the following structure:

if (1 <= num && num <= 7) {
   ...
} else {
   ...
}

Additionally, keep in mind that array indices commence at 0. In the provided example, days[1] would yield 'Tuesday', not 'Monday'.

Answer 3

Answer №2

Here is a helpful answer for you :)

const days = ['Monday', 'Tuesyday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'];

const getDay = (num) => {
  const dayIndex = num - 1;
  if (days[dayIndex]) { // When you pass 0, there is no element at index -1 in the array,
                  // so the if statement will evaluate to false and return null immediately;
    return days[dayIndex];
  }
  return null;
};

console.log(getDay(1)); // Monday
console.log(getDay(7)); // Sunday
console.log(getDay(4)); // Thursday
console.log(getDay(0)); // null

Answer 4

Here is a helpful answer for you :)

const days = ['Monday', 'Tuesyday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'];

const getDay = (num) => {
  const dayIndex = num - 1;
  if (days[dayIndex]) { // When you pass 0, there is no element at index -1 in the array,
                  // so the if statement will evaluate to false and return null immediately;
    return days[dayIndex];
  }
  return null;
};

console.log(getDay(1)); // Monday
console.log(getDay(7)); // Sunday
console.log(getDay(4)); // Thursday
console.log(getDay(0)); // null

What is the best way to set a value to null in JavaScript?

Answer №1

Answer №2

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