tcorral/javascript-challenges-book

Challenge yourself learning and understanding the most obscure and tricky parts of Javascript. http://tcorral.github.io/javascript-challenges-book/

Javascript Challenges

This book will challenge you to learn and understand the most obscure and tricky parts of Javascript.

In order to perform the best that you can I recommend you not to cheat taking a look at solutions before you suggest one.

This book can be used as a learning resource for Javascript training if you want, but please send a tweet recommending us to other people.

I hope you enjoy this book because this is the purpose of this book.

Feedback is welcome.

Thanks a lot to GITBOOK team for it's amazing project to write your own books using Github repos.

javascript-challenges-book's Issues

Book title

On gitbook.io, the book title is "Javascript_Challenges" instead of "Javascript Challenges".

Whole test broken in Firefox

Any step link opens .html file directly,
http://tcorral.github.io/javascript-challenges-book/fooling_around_boolean/README.html
or
https://www.dropbox.com/s/43aczdq8qfnfat6/Screenshot%202014-05-22%2019.13.10.png
for example.
Not an expected behavior for pro-level test of JS knowledge.
FF version is 29.01.

Host it on gitbook.io

This book is really good, would you be interested in hosting it using gitbook.io ?

What is the value of calculateChange ? Input the number value.

Floats Operations Imprecision- solution

Hi!
Thanks for creating javascript challengers book. I click the solution button to find out the answer, then submit the same answer as solution. It displays "ReferenceError: match_answer_and_solution is not defined". I feel confused.

terminator challenge misleading

I assume you want to make the reader think about preventing XSS but your solution doesn't really point the reader to that...

Make the summary accessible more easily

You said feedback welcome, so here it is:
Wouldn't it be nice to have an overview of the book by seeing the summary right after the Introduction in Readme.md?

ReferenceError: __match_answer_and_solution__ is not defined

This errors show up for self invoking functions exercise 2.

How does the bang work when placed in front of an improperly declared function? Such as the test()?

in this function:

function test() { testValue = 3; }();

objects1 solution is suboptimal

You are destroying the semantics of Object.prototype.hasOwnProperty.
A more elegant solution would be:

Object.defineProperty(obj, "name", {  enumerable: false });

input_search unclear

http://tcorral.github.io/javascript-challenges-book/input_search/README.html
Although the keypress event is deprecated it's unclear to me, why there is a performance issue that keyup would solve. Correct me if I'm wrong, but I think the difference is that when holding down a key on the keyboard, the operating system may repeat the character input if you keep it pressed. keypress would be refired in this case while keyup wouldn't. But that's an issue I would usually overcome with a delay, so that I only send the AJAX request after a certain amount of time passed after a keypress.

A possible performance issue I also see is that the #list element is beeing searched over and over again in the loop. Caching would help here.

My "solution" would be:

function delayTimer(delay){
  var timer;
    return function(fn){
      timer = clearTimeout(timer);
      if(fn)
        timer = setTimeout(function() {
           fn();
        },delay);

      return timer;
  };
}
var delayer = delayTimer(500);

$( document ).ready( function() {
  $( '#inputSearch' ).keyup( function() {
      delayer(function() {
        var $list = $( '#list' );
        $.ajax( {
          url: 'http://www.domain.com/search',
          data: this.value,
          success: function ( data )
          {
              var results = data.results;
              $list.empty();
              $.each( data, function ( item ) {
                  $list.append( '<li>' + item + '</li>' );
              } );

          },
          error: function ( xhr, status, error ) {
              console.log( 'Something goes wrong!', status, error.message );
          }
        } );
      } );
  } );
} );

Evaluation framework for the book is borked?

Hey, the site seems to be evaluating answers incorrectly:

Since the answer there should be "you have a syntax error"

fooling_around_boolean_2 explanation unsatisfying

http://tcorral.github.io/javascript-challenges-book/fooling_around_boolean_2/README.html
I don't really understand your description. But the real reason that this doesn't work is because |= is a Bitwise-Or assignment operator and the bitwise representation of {} or [] doesn't evaluate to 1.

Thus using

nResult |= !!aSymbols[i];

should work as desired

Challenge 1.4: Checking Properties - my shorter solution

I think the following solution should be added:

1. It is shorter
2. use of prototype is not something necessary for that specific question spirit, maybe question should be improved

var key,
obj = {
name: 'john',
surname: 'doe'
};

for (key in obj) {
if (obj.hasOwnProperty(key)) {
if (key != "name") {
console.log(key + ' exists in obj');
console.log(key + ': ' + obj[key]);
continue;
}
else console.log(key + " doesn't exist in obj");
}
}