Get any a-Z char using only []()+{}/. in JavaScript (for XSS obfuscation) 16 years ago
The first block (++[[]]) is incrementing in a object but the object is superimposed with other object and the result is error.
the second block [+[]] when [] is object but incrementing + is a number 0 and side-by-side with the block the result is exactly 1.