Question

How i can replace the width in below code with a variable value?

$('<div/>', {
  'class': "formErrorContent",
   width: '13px',
   text: promptText
}).appendTo(prompt);

Like

 var promptWidth = (promptText.length * 5) - (promptText.length/2);
 var promtWidthString  = promptWidth + 'px;'
 var promptContent = $('<div/>', { 'class': "formErrorContent", style: 'width:' +   promtWidthString , text: promptText}).appendTo(prompt);

The above code will end up in a extra

< /br >

at end of the promtText

Answer 1

As you are using appendTo there is no need to store the object in a variable. you can use width for setting width style to the element, also remove the + from your code, note that if you are adding markup, instead of text, you should use html.

$('<div/>', { 
    'class': "formErrorContent", 
     width: promtWidthString,
     html: promptText
}).appendTo(prompt);