Joining String Elements in Multidimensional Array using Javascript

Question

I have a 2D array containing student profiles. Where Column 1 contains First Name, Col2 contains Middle Name, Col3 Last Name and so forth.

What I'm hoping to do is joining text from all three column, convert to upper case, then place back onto Column 1 i.e "FIRSTMIDDLELAST" in cell A1.

My snippet of code is below seems straight forward enough but I'm only very new to JS, upon executing I get an error..

Cannot read property "0" from undefined.

@ line

StudentList[i][0].concat(FistName,MidlName,LastName);

for (var i=0; i<StudentList.length; i++){
      var FistName = StudentList[i][0].valueOf().toUpperCase();
      var MidlName = StudentList[i][0].valueOf().toUpperCase();
      var LastName = StudentList[i][0].valueOf().toUpperCase();

       StudentList[i][0].concat(FistName,MidlName,LastName);
    }

Some help would be greatly appreciated. Thank you so much advance.

UPDATE:

This is a small sample of the Google Spreadsheet where I my array came from ....

First   Middle   Last     Age  Grade  English  Maths
John    Peter    Smith    17   12     A        A
Kevin   Paul     James    16   11     B        C
Kim     Caroline Anderson 15   10     B        A
.... so on

seems your second column is null, put the command debugger; before var FistName = StudentList[i][0].valueOf().toUpperCase();, open your DevTools and check using the console. while the breakpoint is stopped... also seems you're taking the same column for all three names... your should change your StudentList[i][0] for StudentList[i][1] and [2] — andrepaulo
– andrepaulo, Commented Feb 18, 2017 at 6:19
Can you include example of array at Question? What is purpose of .valueOf() call? — guest271314
– guest271314, Commented Feb 18, 2017 at 6:20

Fal · Accepted Answer · 2017-02-18 06:45:14Z

1

the code seems fine, maybe you had wrong array value?

var StudentList = [];
StudentList.push(['First', 'Middle', 'Last']);

document.write('original: ' + StudentList.toString() + '<br/>');
for (var i=0; i<StudentList.length; i++){
  var FistName = StudentList[i][0].valueOf().toUpperCase();
  var MidlName = StudentList[i][1].valueOf().toUpperCase();
  var LastName = StudentList[i][2].valueOf().toUpperCase();


  //StudentList[i][0].concat(FistName,MidlName,LastName);
  StudentList[i][0] = FistName.concat(MidlName,LastName); //i think you mean this
};
document.write('modified: ' + StudentList.toString());

answered Feb 18, 2017 at 6:45

Fal

1346 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

user1488934 Over a year ago

your method works without error!. So why then does StudentList[i][0] = FistName.concat(MidlName,LastName); works yet StudentList[i][0] = FistName + MidlName + LastName; doesn't, so we can learn for future reference.

luiscrjr · Accepted Answer · 2017-02-18 06:41:38Z

0

Assuming your structure is like this (as you described):

var StudentList = [
  ['fname1','mname1','lname1'],
  ['fname2','mname2','lname2'],
  ['fname3','mname3','lname3']
];

Your code could be something like this:

for (var i = 0; i < StudentList.length; i++) {
  var FistName = StudentList[i][0].toUpperCase();
  var MidlName = StudentList[i][1].toUpperCase();
  var LastName = StudentList[i][2].toUpperCase();

  StudentList[i][0] = FistName + MidlName + LastName;
}

/*
[
  [
    "FNAME1MNAME1LNAME1",
    "mname1",
    "lname1"
  ],
  [
    "FNAME2MNAME2LNAME2",
    "mname2",
    "lname2"
  ],
  [
    "FNAME3MNAME3LNAME3",
    "mname3",
    "lname3"
  ]
]
*/

Some points:

you don't need .valueOf() here to get the value;
concat don't modify the actual value, but creates a new String. So, you'll have to assign your result to StudentList[i][0];
you can concatenate strings in JavaScript with + operator;

edited Feb 18, 2017 at 6:41

answered Feb 18, 2017 at 6:37

luiscrjr

7,2783 gold badges28 silver badges28 bronze badges

2 Comments

user1488934 Over a year ago

thanks @mrlew, can't recall why I end up with .valueOf() maybe I was just trying something different to see if it helps. So even after trying your code, I'm still getting error " Cannot set property "0.0" of undefined to "JOHNPETERSMITH"". Though atleast the uppercase and joining functions works, the issue seems to be with inserting the string back into the array.

luiscrjr Over a year ago

the above code works with that structure I posted, since you didnt show your data. The table diagram is not enough. There is no such thing as column in JavaScript. You can have an Array of array (what I wrote). So you have to know your data before doing any operation. Please do a console.log(StudentList) and edit your question with the result (F12 to open console).

Collectives™ on Stack Overflow

Joining String Elements in Multidimensional Array using Javascript

2 Answers 2

1 Comment

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related