往光标所在位置插入值的js代码

/** 
*往输入域中插入字符串(光标所在位置) 
*@param $t document.getElementById('fieldId') 
*@param myValue 要插入的值 
** 
function addSplitToField($t,myValue){ 
if (document.selection) { 
$t.focus(); 
sel = document.selection.createRange(); 
sel.text = myValue; 
$t.focus(); 
}else if($t.selectionStart || $t.selectionStart == '0') { 
var startPos = $t.selectionStart; 
var endPos = $t.selectionEnd; 
var scrollTop = $t.scrollTop; 
$t.value = $t.value.substring(0, startPos) + myValue + $t.value.substring(endPos, $t.value.length); 
this.focus(); 
$t.selectionStart = startPos + myValue.length; 
$t.selectionEnd = startPos + myValue.length; 
$t.scrollTop = scrollTop; 
}else{ 
$t.value += myValue; 
$t.focus(); 
} 
}