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    <p>Of all the programming languages I have used, Javascript has the most confusing scope system and hoisting is a part of that. The outcome is that it is easy to write unpredictable code in JavaScript and you have to be careful with how you write it to make it into the powerful and expressive language it can be.</p> <p>C#, in common with almost every other language, assumes that you will not use a variable until you have declared it. Because it has a compiler it can enforce that by simply refusing to compile if you try to use an undeclared variable. The other approach to this, more often seen in scripting languages, is that if a variable is used without having been declared it is instantiated at first use. This can make it somewhat hard to follow the flow of code and is often used as a criticism of languages that behave that way. Most people who have used languages with block level scope ( where variables only exist at the level where they were declared ) find it a particularly weird feature of Javascript.</p> <p>A couple of big reasons that hoisting can cause problems:</p> <ul> <li>It is absolutely counter-intuitive and makes code harder to read and its behaviour harder to predict unless you are conscious of this behaviour. Hard to read and hard to predict code is far more likely to include bugs. </li> <li>In terms of limiting the number of bugs in your code, limiting the lifetime of your variables can be really helpful. If you can declare the variable and use it in two lines of code, then having ten lines of code in between those two lines gives a lot of opportunities to accidentally affect the behaviour of the variable. There is a lot of information on this in <em>Code Complete</em> - if you haven't read that, I heartily recommend it.</li> <li>There is a classic UX concept of <a href="http://en.wikipedia.org/wiki/Principle_of_least_astonishment" rel="nofollow">the Principle Of Least Astonishment</a> - features like hoisting ( or like the way Javascript handles equality ) tend to break that. People don't often think of user experience when developing programming languages, but actually programmers tend to be quite discerning users and more than a little grumpy when they find themselves routinely caught out by odd features. Javascript is very lucky that it's unique ubiquity in the browser has created a kind of enforced popularity that meant we have to tolerate its many quirks and problematic design decisions.</li> </ul> <p>Finally, I cannot imagine a reason why it would be a useful addition to a language like C#- what possible benefit could it confer?</p>
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    1. POWhy doesn't hoisting exist in C#?
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    1. COI fully agree. I much prefer not using hoisting and it's certainly not something I want to see in C#. It's just good to understand the reasoning behind it.
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