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

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}") <-- (didn't work for me, I don't know why) I found nothing useful. So any help would be very appreciated.

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'

}

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.

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"

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!