Factual, a company that provides location data on places, thinks more apps could make use of its information.

Many smartphone apps have terms and conditions that allow them to collect location data from users—whether or not those apps actually use that information to improve their service. That data could soon be used in some surprising ways, by music or photo apps, for example.

This is a guest post by moderator Alex J. If you see him in the forums, say hello!

When do you need a semicolon? Here's a handy cheat sheet...

Required: When two statements are on the same line

The semicolon is only obligatory when you have two or more statements on the same line:

var i = 0; i++        // <-- semicolon obligatory
                          //     (but optional before newline)
    var i = 0             // <-- semicolon optional
        i++               // <-- semicolon optional
    

Optional: After statements

The semicolon in JavaScript is used to separate statements, but it can be omitted if the statement is followed by a line break (or there’s only one statement in a {block}). A statement is a piece of code that tells the computer to do something. Here are the most common types of statements:

var i;                        // variable declaration
    i = 5;                        // value assignment
    i = i + 1;                    // value assignment
    i++;                          // same as above
    var x = 9;                    // declaration & assignment
    var fun = function() {...};   // var decl., assignmt, and func. defin.
    alert("hi");                  // function call
    

All of these statements can end with a ; but none of them must. Some consider it a good habit to terminate each statement with a ; – that makes your code a little easier to parse, and to compress: if you remove line breaks you needn't worry about several statements ending up unseparated on the same line.

Avoid!

1. After a closing curly bracket

You shouldn’t put a semicolon after a closing curly bracket }. The only exceptions are assignment statements, such as var obj = {};, see above.

// NO semicolons after }:
    if  (...) {...} else {...}
    for (...) {...}
    while (...) {...}
    
    // BUT:
    do {...} while (...);
    
    // function statement: 
    function (arg) { /*do this*/ } // NO semicolon after }
    

2. After the round bracket of an if, for, while or switch statement

It won't harm to put a semicolon after the { } of an if statement (it will be ignored, and you might see a warning that it's unnecessary). But a semicolon where it doesn't belong (such as after the round (brackets) of an if, for, while, or switch statement) is a very bad idea:

if (0 === 1); { alert("hi") }
    
    // equivalent to:
    
    if (0 === 1) /*do nothing*/ ;
    alert ("hi");
    

This code will alert "hi", but not because 0 equals 1, but because of the semicolon. It makes JavaScript think that you have an empty statement there, and everything to the right of it is treated as no longer belonging to the if conditional and thus independent of it.

Of course there's an exception...

An important quirk: inside the () of a for loop, semicolons only go after the first and second statement, never after the third:

for (var i=0; i < 10; i++)  {/*actions*/}       // correct
    for (var i=0; i < 10; i++;) {/*actions*/}       // SyntaxError
    

How to fix your semicolons

The JavaScript syntax proofing tool JSLint, which is built into the Codecademy code editor, does a pretty good job of finding unnecessary semicolons – or missing ones.

It'll show you yellow warning triangles in code lines. Hovering the mouse over a triangle will tell you if there's a missing semicolon or an unnecessary one. You can generally trust those warnings until you develop an intuition of where to use semicolons and where not to.

Conditional comments are gone in IE 10. That's good. IE 10 is a very good browser. Feature detection is a better way to go in nearly all cases. But what if you find some styling situation where you absolutely need to target IE 10? I guess you'll have to do this.

Rogie posted a really simple idea a while back that should still work great for this. Add the User Agent to the <html> element with a tiny bit of JavaScript:

var doc = document.documentElement;
    doc.setAttribute('data-useragent', navigator.userAgent);

IE 10's User Agent string is:

Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)

Which will result in:

<html data-useragent="Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.2; Trident/6.0)">

And you can then style like:

html[data-useragent*='MSIE 10.0'] h1 {
      color: blue;
    }

Check out this Pen!

IE 10 Specific Styles is a post from CSS-Tricks