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web_development

JavaScript string helper class

Riaan Lehmkuhl

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16 Feb 2010CPOL

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Save the following code to a .js file or add to an existing one you might have:function stringHelper() { this.isNullOrEmpty = function(str) { if (null == str) return true; str = this.trim(str); return str.length == 0; } this.trim =...

Save the following code to a .js file or add to an existing one you might have:

C#

function stringHelper() {
    this.isNullOrEmpty = function(str) {
        if (null == str) return true;
        str = this.trim(str);
        return str.length == 0;
    }
    
    this.trim = function(str, chars) {
        return this.ltrim(this.rtrim(str, chars), chars);
    }
 
    this.ltrim = function(str, chars) {
        chars = chars || "\\s";
        return str.replace(new RegExp("^[" + chars + "]+", "g"), "");
    }
    
    this.rtrim = function (str, chars) {
        chars = chars || "\\s";
        return str.replace(new RegExp("[" + chars + "]+$", "g"), "");
    }
    this.return2br = function (str) {
        if (this.isNullOrEmpty(str)) return "";
        return str.replace(/(\r\n|\r|\n)/g, "<br />");
    }
}
var StringHelper = new stringHelper();

To use, just use the StringHelper class instance, e.g.

C#

StringHelper.trim("    this is some text   ");

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Written By

Riaan Lehmkuhl

Software Developer Codely

South Africa

Me, a disorder of the brain that results in a disruption in a person's thinking, mood, and ability to relate to others.

Comments and Discussions

Why not just prototype the trim functions on to the strings themselves?

Helbrax16-Feb-10 9:24

16-Feb-10 9:24

Why not just prototype the trim functions on to the strings themselves? Saves you from having to create a string helper class. Besides, the way you have the class written, if you create more than one, each function is going to be created again, wasting memory.

String.prototype.trim = function() {
...
};

('I am a string').trim();

Re: Why not just prototype the trim functions on to the strings themselves?

Riaan Lehmkuhl16-Feb-10 10:30

16-Feb-10 10:30

The idea is not to create more than one, but to use the existing StringHelper class instance.

Re: Why not just prototype the trim functions on to the strings themselves?

AspDotNetDev16-Feb-10 13:33

16-Feb-10 13:33

Why even create an instance when you can use a prototype?

[Forum Guidelines]

Re: Why not just prototype the trim functions on to the strings themselves?

Riaan Lehmkuhl16-Feb-10 20:05

16-Feb-10 20:05

Why even use a prototype when you can create an instance?
There are several ways to skin a cat.
The benefit of using a prototype is that the function implementations do not reside in every instance of the class. In this case that does not matter because there should always only be one instance (StringHelper) of the stringHelper class.

Dead | X|

Dead | X|

I think the correct question you should have asked should have been:
What was the reason you used this method instead of using a prototype?

Re: Why not just prototype the trim functions on to the strings themselves?

AspDotNetDev16-Feb-10 22:56

16-Feb-10 22:56

It's faster to use prototypes (less syntax). You don't have to pass an instance around or unnecessarily declare a global variable. It's less of a burden on memory to use a prototype rather than have the function declared on each instance. These are basic things one learns when taking an introductory programming course.

[Forum Guidelines]

Re: Why not just prototype the trim functions on to the strings themselves?

Riaan Lehmkuhl16-Feb-10 23:36

16-Feb-10 23:36

Please read my previous reply about the burden on memory you are talking about.

Also using a prototype would not always work with the isNullOrEmpty method because the object that's passed in might not have been initialized as a String object. The prototype property of constructor functions, is used by the new operator, when it creates the new object instance.

This post was all about string manipulation, bet you didn't even read the code beyond the fact that I didn't use the prototype object.
If you dont like it just post an alternate solution Poke tongue | ;-P

Poke tongue | ;-P

that's challenge by the way. Let's share in stead of complaining. Wink | ;)

Wink | ;)

Re: Why not just prototype the trim functions on to the strings themselves?

AspDotNetDev16-Feb-10 23:46

16-Feb-10 23:46

Riaan Lehmkuhl wrote:
Please read my previous reply about the burden on memory you are talking about.

You say there will only be one instance of the class created. Says who? Why not prevent the user from going overboard by using a prototype instead?

Riaan Lehmkuhl wrote:
Also using a prototype would not always work with the isNullOrEmpty method because the object that's passed in might not have been initialized as a String object. The prototype property of constructor functions, is used by the new operator, when it creates the new object instance.

I'm not sure what you mean here. If you provide a prototype for StringHelper (not for String), you should have no problem using it.

Riaan Lehmkuhl wrote:
This post was all about string manipulation, bet you didn't even read the code beyond the fact that I didn't use the prototype object.

Your code is very basic. It took me all of 10 seconds to scan over it.

Riaan Lehmkuhl wrote:
If you dont like it just post an alternate solution

I'm just trying to help you (and others who may read your tip/trick). Why not improve your tip/trick to make use of a prototype? I could do it myself, but I don't want to be responsible for something an author should be responsible for. There are those who like to make those types of edits to tips/tricks, but I'm not one of them (yet).

[Forum Guidelines]

Re: Why not just prototype the trim functions on to the strings themselves?

Riaan Lehmkuhl17-Feb-10 1:17

17-Feb-10 1:17

So help me (and others who may read my tip/trick), take up the challenge. Put your code where your mouth is. The code is so basic, it should not take more than five minutes. WTF | :WTF:

WTF | :WTF:

Just do it!

aspdotnetdev wrote:
If you provide a prototype for StringHelper (not for String), you should have no problem using it.

Now I don't understand. I should not have created the stringHelper object because it would have been better to use prototypes, but now i should provide a prototype for that?

Re: Why not just prototype the trim functions on to the strings themselves?

Helbrax17-Feb-10 3:28

17-Feb-10 3:28

I think what he is saying here, is that if you are going to use a StringHelper class, it's functions should be prototyped. This is not how you do a class in javascript:

function Class() {
   this.foo = function() {
      ....
   }
   this.bar = function() {
      ....
   }
}

This way, every single instance of Class is going to have memory allocated for the foo and bar methods.

If you ARE going to do a string helping class it should(at the very least) be done something like:

function Class() {

}
Class.prototype.foo = function() {
...
}
Class.prototype.bar = function() {
...
}

This way, the methods are prototype, so no massive memory overhead if more than one instance exists, even if your user doesn't stick to your "you only need one instance of this class" philosophy.

Re: Why not just prototype the trim functions on to the strings themselves?

Riaan Lehmkuhl17-Feb-10 6:08

17-Feb-10 6:08

Thumbs Up | :thumbsup:

Re: Why not just prototype the trim functions on to the strings themselves? [modified]

Riaan Lehmkuhl17-Feb-10 8:14

17-Feb-10 8:14

aspdotnetdev - all out of hot air now?

modified on Wednesday, February 17, 2010 2:50 PM

Re: Why not just prototype the trim functions on to the strings themselves?

AspDotNetDev17-Feb-10 9:25

17-Feb-10 9:25

Good morning to you too. Even better than a prototype would be to create static methods on the "class":

HTML

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Untitled Page</title>
    <script type="text/javascript">
    function StringHelper()
    {
    }
    StringHelper.ltrim = function(str, chars)
    {
        chars = chars || "\\s";
        return str.replace(new RegExp("^[" + chars + "]+", "g"), "");
    }
    window.onload = function()
    {
        document.getElementById("div1").innerHTML = "some" + StringHelper.ltrim("    thing");
    }
    </script>
</head>
<body>
    <div id="div1"></div>
</body>
</html>

Let me know if you have any questions.

[Forum Guidelines]

Re: Why not just prototype the trim functions on to the strings themselves?

Riaan Lehmkuhl17-Feb-10 9:59

17-Feb-10 9:59

Thumbs Up | :thumbsup:

Now that's better. Excellent Idea!

Re: Why not just prototype the trim functions on to the strings themselves?

Helbrax24-Feb-10 8:30

24-Feb-10 8:30

If you are going to do it that way, why even declare it as a function at all. Assigning it that way makes declaring StringFunction as a function(read: constructor) misleading, unless you plan to add some "non-static" methods to it as well.

function StringHelper() {

}
StringHelper.ltrim = function() {
   ...
}
var shObject = new StringHelper();
shObject.ltrim()  //this will fail, as there is not ltrim method of the object, only a "static" method

To avoid the confusion, if you don't plan to actually use an object via the constructor, just place it in an object literal.

var StringHelper = {};
StringHelper.ltrim = function() {
   ...
}
StringHelper.ltrim()  //this will succeed

Re: Why not just prototype the trim functions on to the strings themselves?

AspDotNetDev24-Feb-10 8:51

24-Feb-10 8:51

Sounds like a good idea. And while we're at it, we might as well assign the functions like so:

JavaScript

var StringHelper = {
    ltrim: function() {
        // ...
    }
}

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