使用按钮进行文本信息的修改和删除,并从光标指定位置修改文本内容，不使用键盘的退格键。
<!doctype html>
<html lang="en"><head>
<meta charset="UTF-8">
<meta name="Generator" content="EditPlus®">
<meta name="Author" content="">
<meta name="Keywords" content="">
<meta name="Description" content="">
<title>Document</title>
</head>
<body>
<input type="text" id="txt1" value="abcde225544555" >
<input type="button" onclick="doGetCaretPosition()" value="退格">
</body>
<script>
window.onload = function()//文本获取焦点
{
document.getElementById('txt1').focus();
}
function doGetCaretPosition() {//获取光标在文本内容中的index编号
var oField=document.getElementById('txt1')
// Initialize
var iCaretPos = 0;
// IE Support
if (document.selection) {
// Set focus on the element
oField.focus();
// To get cursor position, get empty selection range
var oSel = document.selection.createRange();
// Move selection start to 0 position
oSel.moveStart('character', -oField.value.length);
// The caret position is selection length
iCaretPos = oSel.text.length;
}
// Firefox support
else if (oField.selectionStart || oField.selectionStart == '0')
iCaretPos = oField.selectionStart;
// Return results
alert(iCaretPos);
var valueIndex=iCaretPos;
var strLen=oField.value.length;
if(valueIndex==strLen&&strLen>0){
var changeValue=oField.value.substr(0,strLen-1);
oField.value=changeValue;
}else if(valueIndex!=strLen&&valueIndex>0){
var changeValue=oField.value.substr(0,valueIndex-1)+oField.value.substr(valueIndex);
oField.value=changeValue;
}
//return iCaretPos;
setCursorPosition(oField, (valueIndex-1));
}
function setCursorPosition(ctrl, pos){ //设置光标位置
if(ctrl.setSelectionRange){
ctrl.focus();
ctrl.setSelectionRange(pos,pos);
}else if (ctrl.createTextRange) {
var range = ctrl.createTextRange();
range.collapse(true);
range.moveEnd('character', pos);
range.moveStart('character', pos);
range.select();
}
}
</script>
</html>