Convert Truthy or Falsy values to Boolean in JavaScript

Convert Truthy or Falsy values to Boolean #

To convert a truthy or falsy value to a boolean, pass the value to the boolean object - Boolean(myValue). The boolean object converts the passed in value to true if it's truthy, otherwise it converts it to false.

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const a = Boolean('test');
console.log(a); // 👉️ true

const b = Boolean('');
console.log(b); // 👉️ false

We used the boolean object to convert two strings to booleans.

The boolean object returns false if the passed in value is falsy.

The falsy values in JavaScript are: false, 0, -0, empty string, null, undefined, NaN.

In all other cases, true is returned.

Here are some examples of using the boolean object.

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console.log(Boolean([])); // 👉️ true
console.log(Boolean({})); // 👉️ true
console.log(Boolean('')); // 👉️ false
console.log(Boolean('false')); // 👉️ true
console.log(Boolean(0)); // 👉️ false
console.log(Boolean(100)); // 👉️ true

Note that an empty array and empty object are truthy values, whereas an empty string is falsy.

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const a = !!'test';
console.log(a); // 👉️ true

const b = !!'';
console.log(b); // 👉️ false

The double bang (!!) operator is basically using the logical NOT (!) operator twice.

The logical NOT (!) operator converts a value into a boolean and inverts the result.

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console.log(!'test'); // 👉️ false
console.log(!''); // 👉️ true

When we use the logical NOT (!) operator twice, we:

• convert the value to a boolean and flip it
• flip the boolean again

An easy way to think about it is - we're basically converting a value to a boolean.

Here are some examples.

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console.log(!![]); // 👉️ true
console.log(!!{}); // 👉️ true
console.log(!!''); // 👉️ false
console.log(!!'false'); // 👉️ true
console.log(!!0); // 👉️ false
console.log(!!100); // 👉️ true

Further Reading #

• How to get the Class Name of an Object in JavaScript
• How to Check if a Value is Truthy in JavaScript