Aug
13

Dangerous Bracket Notation for Strings

vjeux Javascript 2009-08-13

The bracket notation for string is incomplete in Javascript and does not work in IE7. This is really painful to migrate to the .charAt(pos) equivalent, this is why i recommend you not to use it.

// Bracket Notation
"Hello World!"[6]
// > "W"
 
// Real Implementation
"Hello World!".charAt(6)
// > "W"

The bracket notation to get a character from a string is a shortcut to .charAt(pos) added by the vast majority of the browsers. However, i would not recommend to use it for several reasons.

This notation does not work in IE7. The first code snippet will return undefined in IE7. If you happen to use the bracket notation for strings all over your code and you want to migrate to .charAt(pos), this is a real pain: Brackets are used all over your code and there's no easy way to detect if that's for a string or an array/object.

You can't set the character using this notation. As there is no warning of any kind, this is really confusing and frustrating. If you were using the .charAt(pos) function, you would not have been tempted to do it.

var string = "Hello World!";
string[6] = '?';
console.log(string);
// > "Hello World!";
If you liked this article, you might be interested in my Twitter feed as well.
 
All Posts
«
»
 

Related Posts

  • October 12, 2011 Intercept and alter <script> include (2)
    For a project, I want to transparently be able to intercept all the included javascript files, edit the AST and eval it. This way I can manipulate all the code of an application just by inserting a custom script. Hook the <script> tag insertion. Download the Javascript file […]
  • September 24, 2011 Javascript: Cyclic Object Detection (16)
    URLON.stringify() suffer from a problem, when passed an object that contains a cycle, it will never stop. This article shows 3 techniques in order to detect if an object is cyclical. Edit the object: Mark In order to detect a cycle in an object, the method we learn at school is to […]
  • September 22, 2011 URLON: URL Object Notation (43)
    #json, #urlon, #rison { width: 100%; font-size: 12px; padding: 5px; height: 18px; color: #560061; } I am in the process of rewriting MMO-Champion Tables and I want a generic way to manage the hash part of the URL (#table__search_results_item=4%3A-slot). I no longer […]
  • January 8, 2010 Javascript – Sorting Table (18)
    For my new project on World of Raids I have to implement a table sorting. The browser not stable sorting and the faster sorting trick add difficulty to the task. String Comparison As mentionned in the Speed Up Javascript Sort() article, using a string as a key to represent each […]
  • December 22, 2011 Javascript – One line global + export (2)
    I've been working on code that works on Browser, Web Workers and NodeJS. In order to export my module, I've been writing ugly code like this one: (function () { /* ... Code that defines MyModule ... */ var all; if (typeof self !== 'undefined') { all = self; // Web […]
Sovrn