Does JavaScript Utilize Short-Circuit Evaluation in Logical Operators?

JavaScript's Short-Circuit Evaluation - A Comprehensive Guide

In programming, short-circuit evaluation refers to the behavior where an expression is evaluated until a result is known, and the rest of the expression is skipped. This mechanism is commonly used in conditional statements to avoid unnecessary computations.

Does JavaScript Support Short-Circuit Evaluation?

Yes, JavaScript does support short-circuit evaluation. As demonstrated in the examples below, the && (AND) and || (OR) operators exhibit this behavior.

Example:

Consider the following JavaScript code:

if (true || foo.foo) {
  // Passes, no errors because `foo` isn't defined.
}

Live Demo: https://jsfiddle.net/iayzejre/

Explanation:

The || operator will immediately return true once the first operand (in this case, true) evaluates to true. Therefore, the expression will pass regardless of whether or not foo.foo is defined, since the second operand is not evaluated.

Example:

Now consider this code:

if (false && foo.foo) {
  // Also passes, no errors because `foo` isn't defined.
}

Live Demo: https://jsfiddle.net/iayzejre/1/

Explanation:

Similarly, the && operator will only evaluate the second operand if the first operand evaluates to true. Since false is always false, the condition fails immediately, and foo.foo is never evaluated.

Workaround for Other Languages

If your coding language does not support short-circuit evaluation, there is a possible workaround using ternary operators. Consider this C# example:

if (true ? true : foo.foo) {
  // Passes without compilation errors.
}

In this case, the ternary operator will immediately return true if the first operand (the true condition) is true. If false, it will evaluate the second operand (the foo.foo expression). However, this workaround may not be suitable for all scenarios and should be used with caution.

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