Calling a Function defined inside another function

问题:

I am calling a function on button click like this:

<input type="button" onclick="outer();" value="ACTION">​

function outer() { 
    alert("hi");       
}

It works fine and I get an alert:

Now when I do like this:

function outer() { 
    function inner() {
        alert("hi");
    }
}

Why don't I get an alert?

Though inner function has a scope available in outer function.

回答1:

The scoping is correct as you've noted. However, you are not calling the inner function anywhere.

You can do either:

function outer() { 

    // when you define it this way, the inner function will be accessible only from 
    // inside the outer function

    function inner() {
        alert("hi");
    }
    inner(); // call it
}

Or

function outer() { 
    this.inner = function() {
        alert("hi");
    }
}

<input type="button" onclick="(new outer()).inner();" value="ACTION">​

回答2:

You could make it into a module and expose your inner function by returning it in an Object.

function outer() { 
    function inner() {
        console.log("hi");
    }
    return {
        inner: inner
    };
}
var foo = outer();
foo.inner();

回答3:

You are not calling the function inner, just defining it.

function outer() { 
    function inner() {
        alert("hi");
    }

    inner(); //Call the inner function

}

回答4:

You can also try this.Here you are returning the function "inside" and invoking with the second set of parenthesis.

function outer() {
  return (function inside(){
    console.log("Inside inside function");
  });
}
outer()();

Or

function outer2() {
    let inside = function inside(){
      console.log("Inside inside");
    };
    return inside;
  }
outer2()();