How Does JavaScript's AND Operator (&&) Behave in Assignment?

JavaScript Assignment and the AND Operator

In JavaScript, the assignment operator can be used in conjunction with various logical operators, including the AND (&&) operator. However, the behavior of the AND operator within an assignment differs from the OR (||) operator.

Behavior of the AND Operator

Unlike the OR operator, which assigns the value of the second operand if the first is falsy, the AND operator assigns:

• The value of the first operand if it is falsy.
• The value of the second operand if the first is truthy.

Specific Examples

Let's consider the following example:

var oneOrTheOther = someOtherVar && "some string";

• If someOtherVar is non-false (truthy): oneOrTheOther will be assigned the value of "some string".
• If someOtherVar is false: oneOrTheOther will be assigned the value of someOtherVar (false).

Falsy Values

Note that falsy values in JavaScript include:

• Null
• Undefined
• NaN (Not a Number)
• 0 (zero)
• An empty string ("")

Any value that is not falsy is considered truthy.

Conclusion

The AND operator within an assignment only assigns the value of the second operand if the first operand is truthy. Otherwise, it assigns the value of the first operand (which must be falsy). This behavior is essential for ensuring correct evaluation and assignment of Boolean and other truthy/falsy values in JavaScript code.

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