Cannot read property 'firstName' of undefined


#1


Cannot see the error ,please help


var bob = {
firstName: "Bob",
lastName: "Jones",
phoneNumber: "(650) 777-7777",
email: "bob.jones@example.com"
};

var mary = {
firstName: "Mary",
lastName: "Johnson",
phoneNumber: "(650) 888-8888",
email: "mary.johnson@example.com"
};

var contacts = [bob, mary];

function printPerson(person) {
console.log(person.firstName + " " + person.lastName);
};

function list() {
var contactsLength = contacts.length;
for (var i = 0; i < contactsLength; i++) {
printPerson(contacts[i]);
}
};
var search=function(lastName)
{
var contactsLength=contacts.length;
for(var i=0;i {
if(lastName===contacts[i].lastName)
{printPerson(bob);}
else
{printPerson(mary);}
}
};
search("Jones");

/*Create a search function
then call it passing "Jones"*/
function add(firstName,lastName,phoneNumber,email){
contacts[contacts.length]={
firstName:firstName,
lastName:lastName,
phoneNumber:phoneNumber,
email:email
}
};
add("Bernard","Lal","(650) 777-8902","berny@example.com");
contacts[contacts.length]=add();
//contacts.push("Bernard","Lal","(650) 777-8902","berny@example.com");
list();


This is the exact error coming:
Oops, try again. You have the following error in your code: TypeError: Cannot read property 'firstName' of undefined


And can someone please tell me why to use push() in the above code.
Thanks :slight_smile:


#2

@sirius_a,
Try it by commenting out

contacts[contacts.length]=add();

like

//contacts[contacts.length]=add();

#3

It worked.
Thanks alot. :smiley:
But could you please explain how it worked without

contacts[contacts.length]=add();


#4

@sirius_a,
Your add() function
is defined as having 4 parameters
and if you call the add() function you will have to provide 4 arguments

the FUNCTION talk

var myFunc = function( param1, param2) {
       //Begin of  anonymous FUNCTION-BODY
       //VARIABLE -myFunc- has an -anonymous function- assigned
       //this -anonymous function- has 2 PARAMETERS param1 and param2
       //param1 and param2 PARAMETERS are used 
       //as -local- VARIABLES throughout the FUNCTION-BODY

      console.log( param1 + " and " + param2 ) ;

      //End of anonymous FUNCTION-BODY
};

If you want to call/execute the anonymous function
you will have to add a pair of parentheses to the variable myFunc
like
myFunc();
As the anonymous function was defined
as having 2 parameters
you have to provide 2 arguments
in our case 2 string VALUES "Alena" and "Lauren"
like
myFunc("Alena","Lauren");

some quotes from the outer-world:

**argument is the value/variable/reference being passed in,
parameter is the receiving variable used within the function/block**

OR

**"parameters" are called "formal parameters",
while "arguments" are called "actual parameters".**

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

function with 1 parameter using return-statement

var myFunction = function( param1 ) {
       //Begin of FUNCTION-BODY
       //myFunction =function= has 1 PARAMETER param1
       //this param1 PARAMETER is used as a -local- VARIABLE
       //throughout the FUNCTION-BODY

      return param1;

      //End of FUNCTION-BODY
      };

you have defined a myFunction function
which takes 1 parameter param1
this param1 parameter is used
as a variable throughout the FUNCTION-BODY.

If you want to call/execute this myFunction function
and this myFunction function was defined
as having 1 parameter param1
you will have to provide 1 argument
in our case a "number VALUE" 4
myFunction( 4 );

some quotes from the outer-world:

**argument is the value/variable/reference being passed in,
parameter is the receiving variable used within the function/block**

OR

**"parameters" are called "formal parameters",
while "arguments" are called "actual parameters".**

============================================

As you are using the return-statement in your myFunction function
you will only get a return-value no-display.
You can however capture this return-value in a variable
and then use the console.log()-method to do a display.

var theResult = myFunction( 4 );
console.log( theResult );

OR directly

console.log( myFunction( 4 ) );

#5

Okay.
But if I use push() and directly put in the values into the array, why wouldn't that work?


#6

@sirius_a
Then extend your add() function with

function add(firstName,lastName,phoneNumber,email){
console.log(firstName);
console.log(lastName);
console.log(phoneNumber);
console.log(email);
 }

#7

Okay.
Thanks again. :slight_smile:


#8

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