两次声明javascript函数

Question

I need to declare a function 2 times with a different treatements let me explain more the overwritting :

function test(var){

    //treatments
}

function test(var){

   alert("something" +var);

}

and here is the HTML code :

<select name="choices" onchange="test(this)">

    <option value="1">test1</option>
    <option value="2">test2</option>

</select>

how can I make them working both without making everything in one function ?

Answer 1

There is no such thing as method/function overriding in javascript. Whichever function is defined last takes precedence. You could split the logic into different functions but you would need some sort of main function that decides which one to use.

Javascript does have switch statements though, so that might be a good fit for your problem. It would be a little neater than a large if/else block. Something like the following might work.

function test(el){
  switch(el.value){
  case 1:
    alert('option 1 selected');
    break;
  case 2:
    alert('Option 2 selected');
    break;
  default:
    alert('Another option was selected');
  }
}

Answer 2

Just imagine you are java script runtime... How will you detect such ambiguity? Answer is no. You can't define functions with same signature in the same scope.

But my advice is to use some kind of "namespaces":

var yourNamespace1 = {

    test: function(var) {
        //treatments
    }
};

var yourNamespace2 = {

    test: function(var) {
        alert("something" +var);
    }
};

It is simple JS objects with defined functions for key "test"

And access the functions by yourNamespace1.test(...) and yourNamespace2.test(...)

Answer 3

You're looking to have different behavior based on the choice in the dropdown. Here's one way to do that:

<select name="choices" onchange="test(this)">

    <option value="1">test1</option>
    <option value="2">test2</option>

</select>

function test(el)
{
   var num = el.options[el.selectedIndex].value;
   if (num == 1)
   {
       // case 1
   }
   else if (num == 2)
   {
       // case 2
   }
}