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!";
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