How do I concatenate a string with a variable

Question

So I am trying to make a string out of a string and a passed variable which is a number   How do I do that   I have something like this   function AddBorder id       document getElementById  horseThumb   id  className  hand positionLeft      So how do I get that  horseThumb  and an id into one string   I tried all the various options  I also googled and besides learning that I can insert a variable in string like this getElementById  horseThumb   id     lt --  didn t work for me  I don t know why  I found nothing useful  So any help would be very appreciated

User · Answer

It s just like you did  And I ll give you a small tip for these kind of silly things  just use the browser url box to try js syntax  for example  write this  javascript alert  test  5  and you have your answer  The problem in your code is probably that this element does not exist in your document    maybe it s inside a form or something  You can test this too by writing in the url  javascript alert document horseThumb 5  to check where your mistake is

User · Answer

This can happen because java script allows white spaces sometimes if a string is concatenated with a number  try removing the spaces and create a string and then pass it into getElementById   example   var str    horseThumb   id   str   str replace    s   s   g       function AddBorder id        document getElementById str  className  hand positionLeft

User · Answer

Your code is correct  Perhaps your problem is that you are not passing an ID to the AddBorder function  or that an element with that ID does not exist  Or you might be running your function before the element in question is accessible through the browser s DOM   To identify the first case or determine the cause of the second case  add these as the first lines inside the function   alert  ID number      id   alert  Return value of gEBI      document getElementById  horseThumb     id      That will open pop-up windows each time the function is called  with the value of id and the return value of document getElementById  If you get undefined for the ID number pop-up  you are not passing an argument to the function  If the ID does not exist  you would get your  incorrect   ID number in the first pop-up but get null in the second   The third case would happen if your web page looks like this  trying to run AddBorder while the page is still loading    lt head gt   lt title gt My Web Page lt  title gt   lt script gt      function AddBorder id                          AddBorder 42         Won t work  the page hasn t completely loaded yet   lt  script gt   lt  head gt    To fix this  put all the code that uses AddBorder inside an onload event handler      Can only have one of these per page window onload   function                 AddBorder 42                  Or can have any number of these on a page function doWhatever               AddBorder 42             if window addEventListener  window addEventListener  load   doWhatever  false   else window attachEvent  onload   doWhatever

User · Answer

Another way to do it simpler using jquery   sample    function add product id           the code to add the product       updating the div  here I just change the text inside the div         You can do anything with jquery  like change style  border etc          added   product id  html  the product was added to list         Where product id is the javascript var and    added   product id  is a div id concatenated with product id  the var from function add    Best Regards

User · Answer

In javascript the     operator is used to add numbers or to concatenate strings  if one of the operands is a string     concatenates  and if it is only numbers it adds them   example   1 2 3    6  1  2 3     123

[javascript] How do I concatenate a string with a variable?

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