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Java Script Trim Function

By Stephen Bucaro

A "trim function" is a bit of code that removes leading and trailing blanks from a character string. You might use a trim function to clean up the data from a user input form before performing further processing on it.

Google the phrase "Java Script Trim" and you'll find that everybody and their grandmother has a Java Script Trim function to offer. Some of these coders think the fewer the lines used, the faster the code will work. Some enjoy being in a continuous state of puzzlement and so they create code like this shown below.

function trim(s)
{
   return s.replace(/^\s*(.*?)\s*$/,"$1");
}

This code uses a regular expression, and although regular expressions are very powerful and useful when used in the proper application, a trim function is not one of them. There are two problems with using a regular expression; a look at the resulting machine code would show that it's about the slowest way to perform this simple function, and since regular expressions are rarely required in general coding, whenever I see them I have to review.

In any case, I offer the following code for a Java Script Trim function. My goal for this code is not to set a speed record or demonstrate my programming prowess, but instead to provide something that is easy to understand so that you might feel confident in using it in your own projects.

// trim leading and trailing spaces
function trim(s)
{
  var myString = s;
  var j = 0;

  // trim front of string
  for(var i = 0; i < myString.length; i++)
  {
    if(myString.charAt(i) != " ")
    {
      break
    }
    else
    {
      j += 1;
    }
  }
  myString = myString.substring(j, myString.length);

  // trim back of string
  j = myString.length;
  for(var i = myString.length - 1; i >= 0; i--)
  {
    if(myString.charAt(i) != " ")
    {
      break
    }
    else
    {
      j -= 1;
    }
  }
  myString = myString.substring(0, j);

  return myString;
}

The above code simply and efficiently removes leading and trailing blanks from a character string. Now if you regular expression lovers are such hot shots, send me a template that (removes not replaces) blanks within a character string.

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