While exploring the polyfill function for Array.includes, I stumbled upon the following lines of code:
// 2. Let len be ? ToLength(? Get(O, "length")).
var len = o.length >>> 0;
// 4. Let n be ? ToInteger(fromIndex).
// (If fromIndex is undefined, this step produces the value 0.)
var n = fromIndex | 0;
The purpose behind these lines of code and the reasoning for implementing them in this manner is what intrigues me.
It appears that the process involves converting a value to a 32-bit integer number for bitwise operations while also utilizing
zero filled right shift >>> with zero as operand, resulting in zero filling and producing a result of zero if the value is undefined
bitwise OR | with zero as operand, which returns the original converted number or zero if the first operand is undefined.
Once converted to a 32-bit integer, the number is returned in a 64-bit float format, typical of JavaScript numbers.
The length of an array corresponds to a positive 32-bit integer, as explained in the documentation for Array#length.
The
lengthproperty of an object, specifically an instance of type `Array, either sets or returns the number of elements within that array. This value is an unsigned, 32-bit integer always greater than the highest index in the array.
var o = {},
fromIndex;
console.log(o.length >>> 0);
console.log(fromIndex | 0);However, the reasoning behind using different methods to achieve the same result remains unclear.
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