Why Does ' [[]][ []] [ []]' Evaluate to '10' in JavaScript?

Unraveling the JavaScript Puzzle: Deciphering " [[]][ []] [ []]"

In JavaScript, the expression " [[]][ []] [ []]" may seem perplexing at first, but a closer examination reveals a series of operations that ultimately return the string "10."

Breaking down the expression, we have:

• [[]][ []] [ []]

Let's dissect the expression step by step:

1. []:

In JavaScript, [] coerces the empty array [] into a number, resulting in 0. This is due to the behavior of the unary operator, which converts its operand to a Number type.

2. [[]][ []]:

This expression returns the inner array ([]) of the outer array [[]].

3. [[]][ []]:

The operator increments the value of its operand by one. Hence, this operation increments the inner array ([)]), which is a falsy value. Incrementing a falsy value in JavaScript returns 1.

4. [ []]:

Similar to [], this expression coerces the empty array [] into a number, resulting in 0 again.

5. 1 0:

Now we have two numbers to add: 1 from the incremented inner array and 0 from the second empty array coercion. The result is 1.

6. 1 [0]:

Interestingly, in JavaScript, [0] is truthy and evaluates to the string "0." When concatenating a string and a number, JavaScript coerces the number to a string. Hence, this operation yields "10."

Therefore, the seemingly enigmatic expression " [[]][ []] [ []]" unravels into a series of type conversions and concatenations, ultimately returning the string "10."

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