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Bada's Coding

Bada's Coding

Short-Circuit Evaluation

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Bada
·Aug 12, 2022·

1 min read

Logical And (&&)

It returns the first falsy value. If there is no falsy value, it returns the last value.

console.log(true && null && 1); // null
console.log(true && 'a' && 1); // 1

Logical Or (||)

It returns the first truthy value. If there is no truthy value, it returns the last value.

console.log(false || 'hi' || undefined); // hi
console.log(false || 0 || null); // null

Use

Please look at the example below.

function add(a, b) {
  return a + b;
}

console.log(true && add(1, 2)); // 3
console.log(false && add(1, 2)); // false
console.log(true || add(1, 2)); // true
console.log(false || add(1, 2)); // 3

In some cases, 'add' function was called to get the data.

Isn't it similar to a 'if' statement?

Below is a more practical example where things in front of the operators can be changed.

 
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