Update ch1.md

The term "global variable" was used when "global object" is called for, on line 235.

types & grammar/ch1.md

@@ -232,7 +232,7 @@ if (!window.atob) {
 
 Unlike referencing undeclared variables, there is no `ReferenceError` thrown if you try to access an object property (even on the global `window` object) that doesn't exist.
 
-On the other hand, manually referencing the global variable with a `window` reference is something some developers prefer to avoid, especially if your code needs to run in multiple JS environments (not just browsers, but server-side node.js, for instance), where the global variable may not always be called `window`.
+On the other hand, manually referencing the global variable with a `window` reference is something some developers prefer to avoid, especially if your code needs to run in multiple JS environments (not just browsers, but server-side node.js, for instance), where the global object may not always be called `window`.
 
 Technically, this safety guard on `typeof` is useful even if you're not using global variables, though these circumstances are less common, and some developers may find this design approach less desirable. Imagine a utility function that you want others to copy-and-paste into their programs or modules, in which you want to check to see if the including program has defined a certain variable (so that you can use it) or not: