Strange javascript operator: expr >>> 0 [duplicate]

>>> is the Zero-fill right shift operator. The >>> 0 is an abuse of the operator to convert any numeric expression to an “integer” or non-numeric expression to zero. Here is what it does:

This operator shifts the first operand the specified number of bits to
the right. Excess bits shifted off to the right are discarded. Zero
bits are shifted in from the left. The sign bit becomes 0, so the
result is always positive.

Here is an explanation of the convert-to-integer behavior which applies to all bitwise operations:

Bitwise operators treat their operands as a sequence of 32 bits (zeros
and ones), rather than as decimal, hexadecimal, or octal numbers.
[…] Bitwise operators perform their operations on such binary
representations, but they return standard JavaScript numerical values.

Together, these statements assert that expr >>> 0 will always return a positive number as follows:

1. expr is cast to a 32-bit integer for bitwise operation
2. >>> 0 has no effect (no bits are shifted)
3. The result is converted to a Number

Here are a few expressions and their outcome:

        1 >>> 0 // 1 -- Number cast to 32-bit integer then back to Number
      "1" >>> 0 // 1 -- String cast to 32-bit integer then back to Number
undefined >>> 0 // 0 -- failed cast yields zero

Other interesting cases:

      1.1 >>> 0 // 1          -- decimal portion gets it
       -1 >>> 0 // 4294967295 -- -1 = 0xFFFFFFFF
                //               Number(0xFFFFFFFF) = 4294967295
      "A" >>> 0 // 0          -- cast failed
    "1e2" >>> 0 // 100        -- 1x10^2 is 100
   "1e10" >>> 0 // 1410065408 -- 1x10^10 is 10000000000
                //               10000000000 is 0x00000002540BE400
                //               32 bits of that number is 0x540BE400
                //               Number(0x540BE400) is 1410065408

Note: you will notice that none of them return NaN.