> For the complete documentation index, see [llms.txt](https://discountry.gitbook.io/es6-for-react/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://discountry.gitbook.io/es6-for-react/expressions-and-operators/logical-operators.md).

# Logical Operators

## Defination

> Logical operators are typically used with Boolean (logical) values. When they are, they return a Boolean value. However, the && and || operators actually return the value of one of the specified operands, so if these operators are used with non-Boolean values, they may return a non-Boolean value.

## Syntax

```javascript
a1 = true  && true      // t && t returns true
a2 = true  && false     // t && f returns false
a3 = false && true      // f && t returns false
a4 = false && (3 == 4)  // f && f returns false
a5 = 'Cat' && 'Dog'     // t && t returns "Dog"
a6 = false && 'Cat'     // f && t returns false
a7 = 'Cat' && false     // t && f returns false
a8 = '' && false        // returns ""
a9 = false && ||        // returns false
```

## Usage

```jsx
function Mailbox(props) {
  const unreadMessages = props.unreadMessages;
  return (
    <div>
      <h1>Hello!</h1>
      {unreadMessages.length > 0 &&
        <h2>
          You have {unreadMessages.length} unread messages.
        </h2>
      }
    </div>
  );
}

const messages = ['React', 'Re: React', 'Re:Re: React'];
ReactDOM.render(
  <Mailbox unreadMessages={messages} />,
  document.getElementById('root')
);
```

## References

* [MDN Logical Operators AND](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Logical_Operators#Logical_AND)


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