C# like trim(),trimStart(),trimEnd() function in javascript

String.prototype.trimStart=function(c)
{
c = c?c:' ';
var i=0;
for(;i<this.length && this.charAt(i)==c; i++);
return this.substring(i);
}
String.prototype.trimEnd=function(c)
{
c = c?c:' ';
var i=this.length-1;
for(;i>=0 && this.charAt(i)==c;i--);
return this.substring(0,i+1);
}
String.prototype.trim=function(c)
{
return this.trimStart(c).trimEnd(c);
}
Example:
" anil soni ".trim()