JavaScript Logical Assignment Operators

المعرفة:: JavaScript الحالة::مؤرشفة المراجع:: The Complete JavaScript Course 2022 From Zero to Expert

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• Introduced in ES2021.
• OR assignment operator (||=): assigns a variable to a variable if that variable is currently falsy.
• Nullish assignment operator (??=): assigns a variable to a variable if that variable is currently null.
• AND assignment operator (&&=): assigns a variable to a variable if that variable is currently truthy.

// Logical Assignment Operators
const rest1 = {
  name: "Capri",
  numGuests: 20,
};
const rest2 = {
  name: "La Piazza",
  owner: "Giovanni Rossi",
};
// Set default number if numGuests doesn't exist
// OR assignment operator
rest1.numGuests = rest1.numGuests || 10; // 20
rest2.numGuests = rest2.numGuests || 10; // 10
// Logical
rest1.numGuests ||= 10; // 20
rest2.numGuests ||= 10; // 10
// Nullish assignment operator (null or undefined)
// Logical
rest1.numGuests ??= 10;
rest2.numGuests ??= 10;
// AND assignment operator
rest1.owner = rest1.owner && "<ANONYMOUS>"; // 'undefined'
rest2.owner = rest2.owner && "<ANONYMOUS>"; // '<ANONYMOUS>'
// Logical
rest1.owner &&= "<ANONYMOUS>"; // nothing happens since rest1.owner isn't true
rest2.owner &&= "<ANONYMOUS>"; // '<ANONYMOUS>'