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JavaScript JavaScript Loops, Arrays and Objects Tracking Data Using Objects The Build an Object Challenge, Part 1

nicolo orcine
nicolo orcine
3,138 Points
Posted by nicolo orcine
nicolo orcine
3,138 Points

Need some clarifications

Hello, when i run this code e get a print in the browser of this one. i don't i understand why i have a print of undefined. thanks.

Students

undefined

Nico

Jessa

Duke

Gilbert

Dukepogi

<!------------------------------------------------------------------------>

var List;

var names;

var achiev = 0;

var earned = 0;

function print (storage){

document.write (storage);

};

var details = [

{Name: "Nico", Track: "Front-end Developer", Achievement: achiev, Points: earned},

{Name: "Jessa", Track: "Accountant", Achievement: achiev, Points: earned},

{Name: "Duke", Track: "CEO", Achievement: achiev, Points: earned},

{Name: "Gilbert", Track: "Manager", Achievement: achiev, Points: earned},

{Name: "Dukepogi", Track: "Chairman", Achievement: achiev, Points: earned}

];

for (var i = 0; i <details.length ; i += 1) {

names += '<p>'+ details[i].Name + '</p>';

}

print(names);

Robert Anthony
Robert Anthony
19,952 Points

Is this ALL the code? Where do you print the word "Students"?

nicolo orcine
nicolo orcine
3,138 Points
nicolo orcine
nicolo orcine
3,138 Points

the word "student" where in the html file. :)

2 Answers

andren
andren
28,558 Points
andren
andren
28,558 Points

It likely comes from the fact that you use += on the names variable without first assigning anything to it. If you assign an empty string to the variable when you create it. Like this:

var names = "";

Then you should not get undefined in the beginning.

The reason this occurs in the first place is that when you use += to add a string to a variable, JavaScript will automatically convert the variable to a string if it is not already defined as such. When an undefined variable (a variable that has no value assigned to it) is converted it gets turned into a string actually containing the word undefined.

By assigning it an empty string you avoid this issue since JavaScript no longer needs to convert the variable before it adds the value.

nicolo orcine
nicolo orcine
3,138 Points
nicolo orcine
nicolo orcine
3,138 Points

Thanks a lot! Very helpful!