method One: Regular replacement recommendation
Personally think the best way. Using regular expressions, this is the core principle.
The following is the original code
Copy Code code as follows:
<script language= "JavaScript" >
<!--
Source: Online Collection
For more visit http://www.jb51.net
Trim (), Ltrim (), RTrim ()
String.prototype.Trim = function ()
{
Return This.replace (/(^\s*) | ( \s*$)/g, "");
}
String.prototype.LTrim = function ()
{
Return This.replace (/(^\s*)/g, "");
}
String.prototype.RTrim = function ()
{
Return This.replace (/(\s*$)/g, "");
}
-->
</SCRIPT>
Let's take a look at what "s/s represents in the JS script.
\s matches any white space character, including spaces, tabs, page breaks, and so on. equivalent to [\f\n\r\t\v].
Please bear in mind that the lowercase s
Second, this method uses the prototype properties of JavaScript
In fact, you do not use this property can be implemented using the function. But this is easier to use.
Let's take a look at how this property is used.
Returns a reference to the object type prototype.
Objectname.prototype
The objectname parameter is the name of the object.
Description
Use the prototype property to provide a set of basic functions for the object's class. The operation of the new instance of the object, "inherit", gives the object a prototype.
For example, to add a method that returns the maximum element value in an array for the array object. To do this, declare the function, add it to the Array.prototype, and use it.
function Array_max () {var i, max = this[0]; for (i = 1; i < this.length; i++) {if (Max < this[i)) max = This[i]; return Max;} Array.prototype.max = Array_max;var x = new Array (1, 2, 3, 4, 5, 6); var y = X.max ();
After the code executes, Y saves the maximum value in the array x, or says 6.
All JScript internal objects have read-only prototype properties. You can add functionality to the prototype as in this example, but the object cannot be given a different prototype. However, user-defined objects can be assigned to a new prototype.
The list of methods and attributes for each internal object in the language reference indicates which parts of the object's prototype and which are not.
Method Two:
Because of the simplicity of the method, there is no example here.
Copy Code code as follows:
JavaScript Go to space function
function LTrim (str) {//Remove the header space of the string
var i;
For (I=0;i if (Str.charat (i)!= "" &&str.charat (i)!= "") a break;
}
str = str.substring (i,str.length);
return str;
}
function RTrim (str) {
var i;
for (i=str.length-1;i>=0;i--) {
if (Str.charat (i)!= "" &&str.charat (i)!= "") break;
}
str = str.substring (0,i+1);
return str;
}
function Trim (str) {
Return LTrim (RTrim (str));
}
Method Three:
This method writes the functions together and achieves different implementations by passing the parameters differently
<HTML> <HEAD> <title>javascript Trim function</title> <script language=javascript> ;! --//****************************************************************//description:sinputstring for input string, itype for type, respectively//0-Remove before and after the space; 1-Go leading blanks; 2-Go tail space//**************************************************************** function Ctrim (sinputstring,itype) {var Stmpstr = ' var i =-1 if (itype = 0 | | itype = 1) {while (stmpstr = = ') {++i stmpstr = Sinputstring.substr ( i,1)} sinputstring = Sinputstring.substring (i)} if (Itype = = 0 | | itype = = 2) {stmpstr = ' i = Sinputstring.len Gth while (stmpstr = = ') {-I stmpstr = Sinputstring.substr (i,1)} sinputstring = Sinputstring.substring (0,i+1)} Return sinputstring}//--></script> </HEAD> <BODY> The string in JavaScript removes the space function (custom):<br> ; SCRIPT language=javascript> <!--var sR0 = Ctrim ("T e s T", 0) var sR1 = Ctrim ("T e s T", 1) var sR2 = CTrIm ("T e s T", 2) document.write ("R0 = '" + sR0 + "' <br>") document.write ("R1 = '" + sR1 + "' <br>") documen T.write ("R2 = '" + sR2 + "' <br>")//--> </SCRIPT> </BODY> </HTML>
[Ctrl + A All SELECT Note: If the need to introduce external JS need to refresh to perform]
