Why does this simple code fail in firefox yet work in every other browser including opera and old IE versions

Question

function T(x){ return (x.textContent) ? function(y){ x.textContent = y; } : function(y){ x.innerText = y; }; }

T(nodeA)('string');
nodeText = T(nodeB);
nodeText('string');

If I change (x.textContent) to (x.textContent !== undefined) it works in firefox. Otherwise I get no errors but nothing happens. Inspecting with firebug shows that T(node); returns function() , which is just baffling to me.

I'm new to javascript but I'm thinking this could be a bug?? I think it can only be true or false, it should be true and return first function but it doesn't return either. Can someone say why?

Answer 1

This won't work if the textContent for the given node is an empty string '' , which evaluates to false . That's why you should do (typeof x.textContent !== 'undefined') instead to ensure the existence of the property.