var MyFunction = function () {     this.myVar = 'something';     var myVar = 'else'; };   What are the pros and cons of the two above, I see them being used.
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What is the scope of variables in javascript? Do they have the same scope inside as opposed to outside a function? Or does it even matter? Also, where are the variables stored if they are defined globally?
1275
I'm using  to go through JavaScript, and it's returning many suggestions to replace == (two equals signs) with === (three equals signs) when doing things like comparing idSele_UNVEHtype.value.length == 0 inside of an if statement.  Is there a performance benefit to replacing == with ===?   Any performance improvement would be welcomed as many comparison operators exist.  If no type conversion takes place, would there be a performance gain over ==?
4613
How can I create or use a global variable in a function?  If I create a global variable in one function, how can I use that global variable in another function? Do I need to store the global variable in a local variable of the function which needs its access?
6641
How far do you go with const?  Do you just make functions const when necessary or do you go the whole hog and use it everywhere?  For example, imagine a simple mutator that takes a single boolean parameter:  void SetValue(const bool b) { my_val_ = b; }   Is that const actually useful?  Personally I opt to use it extensively, including parameters, but in this case I wonder if it's worthwhile?  I was also surprised to learn that you can omit const from parameters in a function declaration but can include it in the function definition, e.g.:  .h file  void func(int n, long l);   .cpp file  void func(const int n, const long l)   Is there a reason for this? It seems a little unusual to me.
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What is the best way(s) to fake function overloading in Javascript?   I know it is not possible to overload functions in Javascript as in other languages.  If I needed a function with two uses foo(x) and foo(x,y,z) which is the best / preferred way:   Using different names in the first place Using optional arguments like y = y || 'default' Using number of arguments Checking types of arguments Or how?
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Which is the right thing to do?  if (myObj['key'] == undefined)   or  if (myObj['key'] == null)   or  if (myObj['key'])
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I've been working on this task (see screenshot).     Here's my answer to it so far:  var sum_pairs=function(ints, s){   //your code here    var ptr_1 = 0,       ptr_2 = 0,       i = 0,       j = 0,       len = ints.length,       j_min = len,       arr_sum = [];    for (i; i &lt; len-1; i++){     for (j = i+1; j &lt; len; j++){       if(ints[i] + ints[j] === s){         if (j &lt; j_min){           j_min = j;           arr_sum = [parseInt(ints[i]), parseInt(ints[j])]         }       }     }   }  return ( (arr_sum.length === 0)? undefined : arr_sum );   }   However, while the tests all pass, it throws an STDERR about 'optimising the code':    How might I be able to optimise my code further?
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For instance, does the compiler know to translate  string s = "test " + "this " + "function";   to  string s = "test this function";   and thus avoid the performance hit with the string concatenation?
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When referencing class variables, why do people prepend it with this? I'm not talking about the case when this is used to disambiguate from method parameters, but rather when it seems unnecessary.  Example:  public class Person {             private String name;      public String toString() {         return this.name;     } }   In toString, why not just reference name as name?  return name;   What does this.name buy?   a stackoverflow question whose code has this pre-pending.
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In c#, is there any difference in the excecution speed for the order in which you state the condition?  if (null != variable) ... if (variable != null) ...   Since recently, I saw the first one quite often, and it caught my attention since I was used to the second one.  If there is no difference, what is the advantage of the first one?
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I am programming in C++ for many years, still I have doubt about one thing. In many places in other people code I see something like:  void Classx::memberfunction() {     this-&gt;doSomething(); }   If I need to import/use that code, I simply remove the this-> part, and I have never seen anything broken or having some side-effects.  void Classx::memberfunction() {     doSomething(); }   So, do you know of any reason to use such construct?  EDIT: Please note that I'm talking about member functions here, not variables. I understand it can be used when you want to make a distinction between a member variable and function parameter.  EDIT: apparent duplicate:
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I wish to know all the pros and cons about using these two methods. In particular the implications on web security.  Thanks.
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In JavaScript, the "this" operator can refer to different things under different scenarios.   Typically in a method within a JavaScript "object", it refers to the current object.  But when used as a callback, it becomes a reference to the calling object.  I have found that this causes problems in code, because if you use a method within a JavaScript "object" as a callback function you can't tell whether "this" refers to the current "object" or whether "this" refers to the calling object.  Can someone clarify usage and best practices regarding how to get around this problem?     function TestObject() {             TestObject.prototype.firstMethod = function(){                       this.callback();                       YAHOO.util.Connect.asyncRequest(method, uri, callBack);              }              TestObject.prototype.callBack = function(o){               // do something with "this"               //when method is called directly, "this" resolves to the current object               //when invoked by the asyncRequest callback, "this" is not the current object               //what design patterns can make this consistent?               this.secondMethod();             }             TestObject.prototype.secondMethod = function() {              alert('test');             }         }
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I quite often see JavaScript with variables that start with a dollar sign. When/why would you choose to prefix a variable in this way?  (I'm not asking about $('p.foo') syntax that you see in jQuery and others, but normal variables like $name and $order)
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In many languages assignments are legal in conditions. I never understood the reason behind this. Why would you write:  if (var1 = var2) {   ... }   instead of:  var1 = var2; if (var1) {   ... }
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How is parseInt() different from valueOf() ?   They appear to do exactly the same thing to me (also goes for parseFloat(), parseDouble(), parseLong() etc, how are they different from Long.valueOf(string) ?  Also, which one of these is preferable and used more often by convention?
14089
I'm creating a function where I need to pass an object so that it can be modified by the function. What is the difference between:  public void myFunction(ref MyClass someClass)   and  public void myFunction(out MyClass someClass)   Which should I use and why?