I use javascript:void(0)
.
Three reasons. Encouraging the use of #
amongst a team of developers inevitably leads to some using the return value of the function called like this:
function doSomething() {
//Some code
return false;
}
But then they forget to use return doSomething()
in the onclick and just use doSomething()
.
A second reason for avoiding #
is that the final return false;
will not execute if the called function throws an error. Hence the developers have to also remember to handle any error appropriately in the called function.
A third reason is that there are cases where the onclick
event property is assigned dynamically. I prefer to be able to call a function or assign it dynamically without having to code the function specifically for one method of attachment or another. Hence my onclick
(or on anything) in HTML markup look like this:
onclick="someFunc.call(this)"
OR
onclick="someFunc.apply(this, arguments)"
Using javascript:void(0)
avoids all of the above headaches, and I haven't found any examples of a downside.
So if you're a lone developer then you can clearly make your own choice, but if you work as a team you have to either state:
Use href="#"
, make sure onclick
always contains return false;
at the end, that any called function does not throw an error and if you attach a function dynamically to the onclick
property make sure that as well as not throwing an error it returns false
.
OR
Use href="javascript:void(0)"
The second is clearly much easier to communicate.
If you think about the Greek roots of the term, it should become obvious.
- Poly = many: polygon = many-sided, polystyrene = many styrenes (a), polyglot = many languages, and so on.
- Morph = change or form: morphology = study of biological form, Morpheus = the Greek god of dreams able to take any form.
So polymorphism is the ability (in programming) to present the same interface for differing underlying forms (data types).
For example, in many languages, integers and floats are implicitly polymorphic since you can add, subtract, multiply and so on, irrespective of the fact that the types are different. They're rarely considered as objects in the usual term.
But, in that same way, a class like BigDecimal
or Rational
or Imaginary
can also provide those operations, even though they operate on different data types.
The classic example is the Shape
class and all the classes that can inherit from it (square, circle, dodecahedron, irregular polygon, splat and so on).
With polymorphism, each of these classes will have different underlying data. A point shape needs only two co-ordinates (assuming it's in a two-dimensional space of course). A circle needs a center and radius. A square or rectangle needs two co-ordinates for the top left and bottom right corners and (possibly) a rotation. An irregular polygon needs a series of lines.
By making the class responsible for its code as well as its data, you can achieve polymorphism. In this example, every class would have its own Draw()
function and the client code could simply do:
shape.Draw()
to get the correct behavior for any shape.
This is in contrast to the old way of doing things in which the code was separate from the data, and you would have had functions such as drawSquare()
and drawCircle()
.
Object orientation, polymorphism and inheritance are all closely-related concepts and they're vital to know. There have been many "silver bullets" during my long career which basically just fizzled out but the OO paradigm has turned out to be a good one. Learn it, understand it, love it - you'll be glad you did :-)
(a) I originally wrote that as a joke but it turned out to be correct and, therefore, not that funny. The monomer styrene happens to be made from carbon and hydrogen, C8H8
, and polystyrene is made from groups of that, (C8H8)n
.
Perhaps I should have stated that a polyp was many occurrences of the letter p
although, now that I've had to explain the joke, even that doesn't seem funny either.
Sometimes, you should just quit while you're behind :-)
Best Answer
Static and dynamic polymorphism are designed to solve different problems, so there are rarely cases where both would be appropriate. In such cases, dynamic polymorphism will result in a more flexible and easier to manage design. But most of the time, the choice will be obvious, for other reasons.
One rough categorisation of the two: virtual functions allow different implementations for a common interface; templates allow different interfaces for a common implementation.