Implementation of TrimStart, TrimEnd, and Trim on javascript in C#_javascript skills

String.prototype.trimStart = function(trimStr){
if(!trimStr){return this;}
var temp = this;
while(true){
if(temp.substr(0,trimStr.length)!=trimStr){
break ;
}
temp = temp.substr(trimStr.length);
}
return temp;
};
String.prototype.trimEnd = function(trimStr){
if(!trimStr){return this;}
var temp = this;
while(true){
if(temp.substr(temp.length-trimStr.length,trimStr.length)!= trimStr){
break;
}
temp = temp.substr(0,temp.length-trimStr.length);
}
return temp;
};
String.prototype.trim = function(trimStr){
var temp = trimStr;
if(!trimStr){temp=" ";}
return this.trimStart(temp).trimEnd(temp);
};