What does !! in js mean?

The !! operator in JavaScript converts any value to a boolean: true for non-zero, non-empty strings, and objects, and false for 0, null, undefined, NaN, and empty strings. It is used to cast to boolean, invert boolean and implement lazy loading.

The meaning of !! operator in JS

!! operation in JS operator is called the double negation operator in JavaScript. It does the following:

Convert any value to a boolean

Take any value as input and the !! operator will convert it Is a Boolean value:

• For non-zero, non-empty strings and any object, the result is true.
• For 0, null, undefined, NaN, and the empty string, the result is false.

Usage Examples

Here are some examples of usage of the !! operators:

console.log(!!0); // false
console.log(!!1); // true
console.log(!!''); // false
console.log(!!"Hello"); // true
console.log(!!null); // false
console.log(!!undefined); // false
console.log(!!NaN); // false

Purpose

!! operator is mainly used for the following purposes:

• Forcing to a Boolean value: can be used Forces any value to be converted to a boolean for use in situations where an explicit boolean value is required.
• Invert a Boolean value: can be used to invert a Boolean value, such as converting true to false and vice versa.
• Implementing lazy loading: can be used to implement lazy loading, where the content of an element is only loaded when it is displayed.

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