常用的一些自定义函数

1 function $id()
2 {
3 var obj,name;
4 if( arguments.length==2 )
5 {
6 obj = arguments[0];
7 name = arguments[1];
8 }else if( arguments.length==1 ){
9 obj = document;
name = arguments[0];
}else{
return alert( "$id have error!" );
}
return obj.getElementById(name);
}

function $selectedOption(obj,selectedValue)
{
for( var i=0;i<obj.options.length;i++ )
{
if( obj.options[i].value == selectedValue )
{
obj.options[i].setAttribute("selected","true");
obj.selectedIndex = i; //这行代码是后来加上去的，原因在ＩＥ中找不到selectedIndex
return;
}
}
}

function $name()
{
var obj,name;
if( arguments.length==2 )
{
obj = arguments[0];
name = arguments[1];
return obj[name]!==undefined ? obj[name]:obj.getElementsByName(name);
}else if( arguments.length==1 ){
obj = document;
name = arguments[0];
return obj.getElementsByName(name);
}else{
return alert( "$name have error!" );
}
}

function $tag()
{
var obj,name;
if( arguments.length==2 )
{
obj = arguments[0];
name = arguments[1];
}else if( arguments.length==1 ){
obj = document;
name = arguments[0];
}else{
return alert( "$tag have error!" );
}
return obj.getElementsByTagName(name);
}

String.prototype.trim = function() {
var str = this,
str = str.replace(/^\\s\\s*/, ''),
ws = /\\s/,
i = str.length;
while (ws.test(str.charAt(--i)));
return str.slice(0, i + 1);
}