Question

I have code as below:

 var s : String = "hello world"
 var xml : XML;
 try {
    xml = new XML(s);
 } catch (e:TypeError) {
    trace("get a typeError");
 }

but I don’t see it gets into the catch block.

Answer 1

XML() accepts anything (*) in its constructor:

XML(value:* = null)

So no, it does not throw a TypeError.

Note you don’t actually need to use the new keyword for creating instances of XML:

var xml:XML = <item>Content</item>;

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This may also be of interest for you – from XML() – Top level function:

XML()
Converts an object to an XML object.

The following table describes return values for various input types.