What is going on here? Just when I thought I knew JS inside and out, this gem comes up.
String.prototype.doNothing = function() {
return this;
};
alert(typeof 'foo'.doNothing()) // object
alert(typeof 'foo') // string
This is breaking some things that expect a string, such as jQuery's .text(str) method.
Here's a thorough overview of the this keyword. Basically, JavaScript converts it into an object, if it wasn't one.
The following steps are performed when
control enters the execution context
for function code contained in
function object F, a caller provided
thisValue, and a caller provided
argumentsList:
- If the function code is strict code, set the ThisBinding to
thisValue.
- Else if thisValue is null or undefined, set the ThisBinding to the
global object.
- Else if Type(thisValue) is not Object, set the ThisBinding to
ToObject(thisValue).
- Else set the ThisBinding to thisValue
Same thing happens to Numbers and Booleans. A similar DoNothing function would return a type of object.
