JavaScript quirk 4: unknown variable names create global variables
[This post is part of a series on JavaScript quirks.]
Thankfully, you get a warning in ECMAScript 5 strict mode [1]:
Reference:
Normally, JavaScript automatically creates a global variable if you use an unknown variable name:
> function f() { foo = 123 }
> f()
> foo
123
Thankfully, you get a warning in ECMAScript 5 strict mode [1]:
> function f() { 'use strict'; foo = 123 }
> f()
ReferenceError: foo is not defined
Reference:
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