https://github.com/github/fetch/blob/d1d09fb8039b4b8c7f2f5d6c844ea72d8a3cefe6/fetch.js#L1-L5
I'm not sure if I'm reading this wrong, but it seems like the second global is shadowed by the var global declaration. After hoisting, the equivalent code is
var global; // default undefined
global =
(typeof globalThis !== 'undefined' && globalThis) ||
(typeof self !== 'undefined' && self) ||
(typeof global !== 'undefined' && global) ||
{}Because of hoisting, the global gets evaluated as false in all environments:
(typeof global !== 'undefined' && global)
// becomes
(typeof undefined !== 'undefined' && global)
// becomes
('undefined' !== 'undefined' && undefined)
// becomes
(false && undefined)
// becomes
falseI think the intent was to access the global object, if it exists.
We might have to capture it to a variable, oldGlobal, first, but the hoisting of global prevents us from doing this easily.
For example, the following wouldn't work because oldGlobal and global declarations are hoisted.
var oldGlobal = global; // === undefined
var global =
(typeof globalThis !== 'undefined' && globalThis) ||
(typeof self !== 'undefined' && self) ||
(typeof oldGlobal !== 'undefined' && oldGlobal) ||
{}The only solution I can think of that preserves the variable name, global, is to wrap the code in an IIFE to prevent hoisting above oldGlobal. The typeof global is also moved up to oldGlobal to prevent errors on environments that don't global defined.
var oldGlobal = typeof global !== 'undefined' && global
(function () {
var global =
(typeof globalThis !== 'undefined' && globalThis) ||
(typeof self !== 'undefined' && self) ||
oldGlobal ||
{}
// rest of the code...
})()An alternative solution is to rename global to some other name.
https://github.com/github/fetch/blob/d1d09fb8039b4b8c7f2f5d6c844ea72d8a3cefe6/fetch.js#L1-L5
I'm not sure if I'm reading this wrong, but it seems like the second
globalis shadowed by thevar globaldeclaration. After hoisting, the equivalent code isBecause of hoisting, the
globalgets evaluated asfalsein all environments:I think the intent was to access the
globalobject, if it exists.We might have to capture it to a variable,
oldGlobal, first, but the hoisting ofglobalprevents us from doing this easily.For example, the following wouldn't work because
oldGlobalandglobaldeclarations are hoisted.The only solution I can think of that preserves the variable name,
global, is to wrap the code in an IIFE to prevent hoisting aboveoldGlobal. Thetypeof globalis also moved up tooldGlobalto prevent errors on environments that don'tglobaldefined.An alternative solution is to rename
globalto some other name.