Learn
Conditional Statements
Truthy and Falsy

Let’s consider how non-boolean data types, like strings or numbers, are evaluated when checked inside a condition.

Sometimes, you’ll want to check if a variable exists and you won’t necessarily want it to equal a specific value — you’ll only check to see if the variable has been assigned a value.

Here’s an example:

let myVariable = 'I Exist!'; if (myVariable) { console.log(myVariable) } else { console.log('The variable does not exist.') }

The code block in the if statement will run because myVariable has a truthy value; even though the value of myVariable is not explicitly the value true, when used in a boolean or conditional context, it evaluates to true because it has been assigned a non-falsy value.

So which values are falsy— or evaluate to false when checked as a condition? The list of falsy values includes:

  • 0
  • Empty strings like "" or ''
  • null which represent when there is no value at all
  • undefined which represent when a declared variable lacks a value
  • NaN, or Not a Number

Here’s an example with numbers:

let numberOfApples = 0; if (numberOfApples){ console.log('Let us eat apples!'); } else { console.log('No apples left!'); } // Prints 'No apples left!'

The condition evaluates to false because the value of the numberOfApples is 0. Since 0 is a falsy value, the code block in the else statement will run.

Instructions

1.

Change the value of wordCount so that it is truthy. This value should still be a number.

After you make this change and run your code, 'Great! You've started your work!' should log to the console.

2.

Change the value of favoritePhrase so that it is still a string but falsy.

After you make this change and run your code, 'This string is definitely empty.' should log to the console.

Folder Icon

Take this course for free

Already have an account?