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-rw-r--r--javascript.html.markdown37
1 files changed, 27 insertions, 10 deletions
diff --git a/javascript.html.markdown b/javascript.html.markdown
index 588ea86d..34ba9b47 100644
--- a/javascript.html.markdown
+++ b/javascript.html.markdown
@@ -64,7 +64,7 @@ doStuff()
// There are three special not-a-real-number values:
Infinity; // result of e.g. 1/0
-Infinity; // result of e.g. -1/0
-NaN; // result of e.g. 0/0
+NaN; // result of e.g. 0/0, stands for 'Not a Number'
// There's also a boolean type.
true;
@@ -189,7 +189,7 @@ myObj.myFourthKey; // = undefined
///////////////////////////////////
// 3. Logic and Control Structures
-// The syntax for this section is almost identical to Java's.
+// The syntax for this section is almost identical to Java's.
// The `if` structure works as you'd expect.
var count = 1;
@@ -218,6 +218,26 @@ for (var i = 0; i < 5; i++){
// will run 5 times
}
+//The For/In statement loops iterates over every property across the entire prototype chain
+var description = "";
+var person = {fname:"Paul", lname:"Ken", age:18};
+for (var x in person){
+ description += person[x] + " ";
+}
+
+//If only want to consider properties attached to the object itself,
+//and not its prototypes use hasOwnProperty() check
+var description = "";
+var person = {fname:"Paul", lname:"Ken", age:18};
+for (var x in person){
+ if (person.hasOwnProperty(x)){
+ description += person[x] + " ";
+ }
+}
+
+//for/in should not be used to iterate over an Array where the index order is important.
+//There is no guarantee that for/in will return the indexes in any particular order
+
// && is logical and, || is logical or
if (house.size == "big" && house.colour == "blue"){
house.contains = "bear";
@@ -231,8 +251,8 @@ var name = otherName || "default";
// The `switch` statement checks for equality with `===`.
-// use 'break' after each case
-// or the cases after the correct one will be executed too.
+// use 'break' after each case
+// or the cases after the correct one will be executed too.
grade = 'B';
switch (grade) {
case 'A':
@@ -393,7 +413,7 @@ var doubler = product.bind(this, 2);
doubler(8); // = 16
// When you call a function with the `new` keyword, a new object is created, and
-// made available to the function via the this keyword. Functions designed to be
+// made available to the function via the `this` keyword. Functions designed to be
// called like that are called constructors.
var MyConstructor = function(){
@@ -475,9 +495,6 @@ myNumber === myNumberObj; // = false
if (0){
// This code won't execute, because 0 is falsy.
}
-if (Number(0)){
- // This code *will* execute, because Number(0) is truthy.
-}
// However, the wrapper objects and the regular builtins share a prototype, so
// you can actually add functionality to a string, for instance.
@@ -519,12 +536,12 @@ more about how to use JavaScript in web pages, start by learning about the
[Document Object
Model](https://developer.mozilla.org/en-US/docs/Using_the_W3C_DOM_Level_1_Core)
-[Learn Javascript by Example and with Challenges](http://www.learneroo.com/modules/64/nodes/350) is a variant of this reference with built-in challenges.
+[Learn Javascript by Example and with Challenges](http://www.learneroo.com/modules/64/nodes/350) is a variant of this reference with built-in challenges.
[JavaScript Garden](http://bonsaiden.github.io/JavaScript-Garden/) is an in-depth
guide of all the counter-intuitive parts of the language.
-[JavaScript: The Definitive Guide](http://www.amazon.com/gp/product/0596805527/) is a classic guide / reference book.
+[JavaScript: The Definitive Guide](http://www.amazon.com/gp/product/0596805527/) is a classic guide / reference book.
In addition to direct contributors to this article, some content is adapted
from Louie Dinh's Python tutorial on this site, and the [JS