Merge pull request #64 from mobify/effective-js-ch1

Adding a few new rules based on our book club meeting!

Author: jansepar

javascript/README.md

@@ -88,6 +88,21 @@ var length = items.length;
 var name = 'foo';
 ````
 
+##Use semi-colons
+
+There are many more ways that things can break *without* semi-colons then *with* semi-colons.
+Use semi-colons!
+
+```javascript
+// bad
+a = b
+f() // this will evaluate to `a = b f()`, which will be a parse error
+
+// good
+a = b;
+f();
+```
+
 ##Use function expressions over function declarations
 
 The function expression is clearly recognisable as what it really is (a variable with a function value). Additionally, it helps organize code so that all variable declarations appear at the top of a file, and invocations follow. This gives some predictablity when others are reading your code, allowing for a more consistent structure.
@@ -351,3 +366,17 @@ var title = $('h1');
 // good: later on in the code, people will know that they can use jQuery/Zepto on this object
 var $title = $('h1');
 ````
+
+##Always use `===` over `==`
+
+`==` does [implicit coercions](http://dorey.github.io/JavaScript-Equality-Table/), which can
+cause a number of unexpected issues.
+We always prefer `===` over `==`
+
+```javascript
+// bad
+if ("0" == false) {console.log('foo')} // this will console log! bad!
+
+// good
+if ("0" === false) {console.log('foo')}
+```