Issue

This Content is from Stack Overflow. Question asked by Faiz

Hey guys I am new to JavaScript and learning Objects in JavaScript ,
while i was printing a function value from an object the value gets printed along with a undefined value.

I was just trying to concatenate two string in a function and printing it.
I am not getting any undefined value if I just try to concatenate the string with console.log
but the issue arises when I try to concatenate through a function in a object.

let user = {
    firstname:'faiz',
    lastname:'mohammed',
    fun : function()  {
        let full_name = (this.firstname + " " + this.lastname);
        console.log(full_name);
        },

}


console.log(user.fun());

the output is :

PS C:UsersfaizkOneDriveDesktopWEBDEVJS> node objects.js
faiz mohammed
undefined
PS C:UsersfaizkOneDriveDesktopWEBDEVJS>

when I just console log it I am not getting any undefined values :

console.log(user.firstname + " " + user.lastname);

output:

PS C:UsersfaizkOneDriveDesktopWEBDEVJS> node objects.js
faiz mohammed
PS C:UsersfaizkOneDriveDesktopWEBDEVJS>

Solution

Your fun function doesn’t return anything so console.log(user.fun()) prints undefined

Either return something:

function()  {
  let full_name = (this.firstname + " " + this.lastname);
  return full_name
},

console.log(user.fun());

or don’t use console.log

function()  {
  let full_name = (this.firstname + " " + this.lastname);
  console.log(full_name);
},

user.fun();

This Question was asked in StackOverflow by Faiz and Answered by Konrad Linkowski It is licensed under the terms of CC BY-SA 2.5. - CC BY-SA 3.0. - CC BY-SA 4.0.