Undefined string in javascript forEach output

Question

var tmu, categories = [['Morning','am'],['Evening','pm']], 
days = ['mon', 'tue', 'wen', 'thu', 'fri', 'sat', 'sun'],
fullDay, i;

tmu += '<table>';

categories.forEach(function(ele){ 
tmu += '<tr id="periodTitle">';
tmu += '<td colspan=7 style="text-align:center;">'+ele[0]+'</td>';
tmu += '</tr>';
for(i = 0; i <= 6; i++){
tmu += '<td id="'+days[i]+'-'+ele[1]+'">x</td>';    
}        
});
tmu += "</table>";
console.log(tmu);

I am trying to write some code to loop through some table creation however it keeps adding an undefined text to the beginning of the loop and I'm not sure why, everything else works great. Any ideas on how this could happen?

The fiddle link is here. Thanks for any help in advance!!

RobH · Accepted Answer · 2014-01-24 09:02:00Z

2

This will fix it:

var tmu = '';

As you are declaring the variable but not assigining a value, tmu will be undefined and when you do tmu += '<table>';, tmu will be coerced to a string - i.e. undefined.

answered Jan 24, 2014 at 9:02

RobH

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Comments

semirturgay · Accepted Answer · 2014-01-24 09:04:22Z

0

initialize tmu as string see the example

**var tmu=''**, categories = [['Morning','am'],['Evening','pm']], 
days = ['mon', 'tue', 'wen', 'thu', 'fri', 'sat', 'sun'],
fullDay, i;

tmu += '<table>';

categories.forEach(function(ele){ 
    tmu += '<tr id="periodTitle">';
    tmu += '<td colspan=7 style="text-align:center;">'+ele[0]+'</td>';
    tmu += '</tr>';
    for(i = 0; i <= 6; i++){
    tmu += '<td id="'+days[i]+'-'+ele[1]+'">x</td>';    
    }        
});
    tmu += "</table>";
   console.log(tmu);

answered Jan 24, 2014 at 9:04

semirturgay

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Comments

Joeri · Accepted Answer · 2014-01-24 09:06:43Z

0

You need to remove the + in the following rule:

tmu += '<table>';

Change the rule to this and the undefined is gone:

tmu = '<table>';

answered Jan 24, 2014 at 9:06

Joeri

1

Comments

Fabrizio Calderan · Accepted Answer · 2014-01-24 09:08:26Z

0

When you use tmu for the first time, use a simple assignment

tmu = '<table>';

Right now your instruction tmu += '<table>' is a shortcut for tmu = tmu + '<table>': so, you are doing a string concatenation and your tmu variable on the right side of this assignment will be evaluated as a string, which value has to be undefined, since no previous assignment was done.

edited Jan 24, 2014 at 9:08

answered Jan 24, 2014 at 9:03

Fabrizio Calderan

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