When I call function hi()() with double brackets the function displays hi output and it will also give error saying, that hi is not function.
<html>
<head></head>
<script>
function hello()
{
document.write("hello");
}
function hi()
{
document.write("hi");
return "hello";
}
hi()();
</script>
</html>
What is the meaning of using ()() with function name?
The double parenthesis would have been useful if hi had returned a function instead of its name, like in
function hi(){
return hello;
}
hi()();
That's probably what was the intent.
window[hi()](); :P
Putting () after something that evaluates to a function will call that function. So, hi() calls the function hi. Assuming hi returns a function then hi()() will call that function.
Example:
function hi(){
return function(){return "hello there";};
}
var returnedFunc = hi(); // so returnedFunc equals function(){return "hello there";};
var msg = hi()(); // so msg now has a value of "hello there"
If hi() doesn't return a function, then hi()() will produce an error, similar to having typed something like "not a function"(); or 1232();.
()() means calling a function and if returns another function second parenthesis will call it.Please find below example :
function add(x){
return function(y){
return x+y;
}
}
add(3)(4)
output: 7
in above case add(4) will be called for add function and add(3) will be called for returned function. here value of parameter x is 3 and parameter y is 4.
Please note : we use parenthesis for function call.
The return value of this function is a string which is not a callable object.
function hi()
{
document.write("hi");
return "hello"; // <-- returned value
}
But if you want to call this function multiple times you can use a for-loop or some things else.
Example of hi()():
function hi(){
return function(){ // this anonymous function is a closure for hi function
alert('some things')
}
}
JS Fiddle: here
If you want to call hello function immediately after hi try this:
function hi()
{
document.write("hi");
return hello; //<-- no quote needed
// In this context hello is function object not a string
}
You can use eval() to execute it even if it's string : eval(hi()+'()');
window[hi()]()