adding tricky questions

Author: rohan-paul

Javascript/Tricky-JS-Problems/2020-10-08-16-50-10.png

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+![](2020-10-08-16-50-10.png)
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+#### Ans - if you are not using strict mode), the output of the code snippet would be:
+
+![](2020-10-08-16-51-07.png)
+
+### Explanations
+
+Since both a and b are defined within the enclosing scope of the function, and since the line they are on begins with the var keyword, most JavaScript developers would expect typeof a and typeof b to both be undefined in the above example.
+
+However, that is not the case. The issue here is that most developers incorrectly understand the statement var a = b = 3; to be shorthand for:
+
+![](2020-10-08-16-59-10.png)
+
+But in fact, var a = b = 3; is actually shorthand for:
+
+![](2020-10-08-16-59-22.png)
+
+As a result (if you are not using strict mode), the output of the code snippet would be:
+
+![](2020-10-08-16-59-37.png)
+
+But how can b be defined outside of the scope of the enclosing function? Well, since the statement var a = b = 3; is shorthand for the statements b = 3; and var a = b;, b ends up being a global variable (since it is not preceded by the var keyword) and is therefore still in scope even outside of the enclosing function.
+
+Note that, in strict mode (i.e., with use strict), the statement var a = b = 3; will generate a runtime error of ReferenceError: b is not defined, thereby avoiding any headfakes/bugs that might othewise result. (Yet another prime example of why you should use use strict as a matter of course in your code!)