"Undefined" coming as output of an array

Question

I am newbie to Javascript and the syntax just bugs me. The output is giving me undefined as an alert after every function declaration output.

let func=[
    {
        sayHi:function(){
            alert('hello');
        },
        saybi:function(){
            alert('Bye');
        }
    },
    {
        sayName:function(name){
            alert('Hii !! ', +name);
        },
        askName:function(){
            alert("What's your name ??");
        }
    }
];

alert(func[0].sayHi());

let name=prompt("What's your name ?","");
if(name!="")
{
    alert(func[1].sayName(name));
}
else{
    alert(func[1].askName());
}

Actually if u notice i just gave a comma between so func[1] is defined. The thing is that the output does come but after that undefined comes consequently — Johnny Depp
– Johnny Depp, Commented May 1, 2019 at 22:32

zmag · Accepted Answer · 2019-05-01 22:37:30Z

2

functions in func array call alert function. But you have called alert again after invoking a function like alert(func[0].sayHi()).

You should call function like below:

let func = [{
    sayHi: function() {
      alert('hello');
    },
    saybi: function() {
      alert('Bye');
    }
  },
  {
    sayName: function(name) {
      alert('Hii !! ' + name);
    },
    askName: function() {
      alert("What's your name ??");
    }
  }
];

func[0].sayHi();

let name = prompt("What's your name ?", "");
if (name != "") {
  func[1].sayName(name);
} else {
  func[1].askName();
}

Update: I've fixed sayName function to work properly.

edited May 1, 2019 at 22:37

answered May 1, 2019 at 22:32

zmag

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2 Comments

Milan Velebit Over a year ago

Or just return the strings (either 'hello' or 'bye') from those functions with an alert call below. But your answer is clearer I guess. The overall point is that those functions returned nothing, hence the undefined after calling alert with those functions as parameters.

Johnny Depp Over a year ago

Thanks !! It helped. Keep helping us newbies. :p

niry · Accepted Answer · 2019-05-01 22:48:01Z

2

You don't need to wrap every function call with alert() as those functions returns undefined and confuses you. Also alert() takes one argument, so the comma (',') there isn't helping.

Try this:

let func = [
    {
      sayHi: function(){
        alert('hello');
      },
      saybi: function(){
        alert('Bye');
      },
    },{
      sayName: function(name) {
        alert('Hi !! ' + name);
      },
      askName: function() {
        alert("What's your name ??");
      },
    }];

func[0].sayHi();

let name = prompt("What's your name ?", "");
if (name != "") {
    func[1].sayName(name);
} else {
    func[1].askName();
}

edited May 1, 2019 at 22:48

answered May 1, 2019 at 22:39

niry

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1 Comment

Johnny Depp Over a year ago

Great !! Thanks for Help.

Kai Lehmann · Accepted Answer · 2019-05-01 22:28:46Z

0

It works perfect. sayHi() returns nothing so it returns undefined. That is it what you are alerting in the last line.

answered May 1, 2019 at 22:28

Kai Lehmann

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