if statement strange outcome

[jimfog]

Take a look at this code here:function john(){if(window.getSelection){alert("hi")};}john();Normally it should output an alert box ONLY when there is a selection in the page.Nonetheless, it outputs the alert box even when nothing is selected.Is that normal?I did my tests in the firebug console.

[ShadowMage]

Take a look at this code here:function john(){if(window.getSelection){alert("hi")};}john();Normally it should output an alert box ONLY when there is a selection in the page.Nonetheless, it outputs the alert box even when nothing is selected.Is that normal?I did my tests in the firebug console.

Yes, that is normal. What you are actually testing for is the existence of the getSelection method, not whether there is a selection. If you add parens to getSelection, it should test whether there is a selection on the page:if (window.getSelection()) {

[jimfog]

Yes, that is normal. What you are actually testing for is the existence of the getSelection method, not whether there is a selection. If you add parens to getSelection, it should test whether there is a selection on the page:if (window.getSelection()) {

The problem continues, despite the revised code.Here is the revised code:function john(){if(window.getSelection()){alert("hi")};}john();Again, i get the alert box.What might be wrong?

[ShadowMage]

Perhaps try converting to a string and testing against an empty string?if (window.getSelection().toString() == '') {

[jeffman]

Yeah, window.getSelection() returns an object, not a string, so it always evaluates to Boolean true.

[thescientist]

always know your enemyhttps://developer.mozilla.org/en/DOM/window.getSelection

[ShadowMage]

Yeah, window.getSelection() returns an object, not a string, so it always evaluates to Boolean true.

Not sure why, but I was thinking the toString method should be automatically called when testing it in the if statement. After thinking about it, I realized that isn't the case. It should only be called when the object is used as a string (for example, alert(window.getSelection()); )

[jeffman]

I'll say it again. Selections and text ranges are a PITA. Part of the problem is the way they can cross nodes. The DOM is really not set up to handle that, and the methods and properties that do exist are extremely weird.

[jimfog]

I'll say it again. Selections and text ranges are a PITA. Part of the problem is the way they can cross nodes. The DOM is really not set up to handle that, and the methods and properties that do exist are extremely weird.

Finally, the following code worked:function john(){if(window.getSelection()==0){alert("hi")};}john();I did not know the objects are evaluated to boolean values.One mistake i was doing is that instead "0" i tested again "false"(if(window.getSelection()==false)).I checked the tutorials and saw the mistake.Thanks.