onclientClick imageButton return false doesn't work + Answer

I've search about 30min about that.

Calling this didn't work. An alert (a()) would return false but postback anyway.

function a()
{
   var a = new Boolean();
   return a;
}

But that worked, didn't postback:

function a()
{
   var开发者_StackOverflow社区 a = new Boolean();
   a = false;
   return a;
}

How are you placing the OnClientClick? A Javascript return false and an .NET return false are not the same. If your code is

<asp:ImageButton runat="server" OnClientClick="a()" />

then only javascript returns false. let .NET know the response using return:

<asp:ImageButton runat="server" OnClientClick="return a()" />

Most likely, the code that is consuming your function is expecting false not "falsey". If the object new Boolean() is coerced to a boolean value, it will return false. But, the object new Boolean() is not the same as the value false.

new Boolean() == false; // this is true
new Boolean() === false; // this is false!

Most likely, the consuming code is doing an === comparison, not an == comparison. Just do:

function a()
{
    var b = false;
    return b;
}

Boolean is an object, you have to return

function a()
{
   var a = new Boolean();
   return a.valueOf();
}

If a method doesn't return anything, it technically returns "falsey", so to avoid ambiguity browsers require "real false" to be returned. So in your case you can do this:

function a()
{
   var a = new Boolean();
   return !!a;
}

!! will cast your value to real boolean

in this function

function a()
{
   var a = new Boolean();
   return a;
}

You are declaring var a = new Boolean(); and returning the Boolean object NOT VALUE
You type cast it as Boolean but did not set a value which means it is undefined.

in your function

function a()
{
   var a = new Boolean();
   a = false;
   return a;
}

You are assigning a as a Boolean object and then reassigning it as a Boolean value of false and returning the Boolean variable false;

Also you can do this.

function a()
{
   return false;
}