javascript获取以及设置光标位置

一. 获取光标位置：

// 获取光标位置
function getCursortPosition (textDom) {
var cursorPos = 0;
if (document.selection) {
// IE Support
textDom.focus ();
var selectRange = document.selection.createRange();
selectRange.moveStart ('character', -textDom.value.length);
cursorPos = selectRange.text.length;
}else if (textDom.selectionStart || textDom.selectionStart == '0') {
// Firefox support
cursorPos = textDom.selectionStart;
}
return cursorPos;
}

二. 设置光标位置：

// 设置光标位置
function setCaretPosition(textDom, pos){
if(textDom.setSelectionRange) {
// IE Support
textDom.focus();
textDom.setSelectionRange(pos, pos);
}else if (textDom.createTextRange) {
// Firefox support
var range = textDom.createTextRange();
range.collapse(true);
range.moveEnd('character', pos);
range.moveStart('character', pos);
range.select();
}
}

三. 获取选中文字：

// 获取选中文字
function getSelectText() {
var userSelection, text;
if (window.getSelection) {
// Firefox support
userSelection = window.getSelection();
} else if (document.selection) {
// IE Support
userSelection = document.selection.createRange();
}
if (!(text = userSelection.text)) {
text = userSelection;
}
return text;
}

四. 选中特定范围的文本：

/**
* 选中特定范围的文本
* 参数：
*     textDom  [JavaScript DOM String] 当前对象
*     startPos  [Int]  起始位置
*     endPos  [Int]  终点位置
*/
function setSelectText(textDom, startPos, endPos) {
var startPos = parseInt(startPos),
endPos = parseInt(endPos),
textLength = textDom.value.length;
if(textLength){
if(!startPos){
startPos = 0;
}
if(!endPos){
endPos = textLength;
}
if(startPos > textLength){
startPos = textLength;
}
if(endPos > textLength){
endPos = textLength;
}
if(startPos < 0){
startPos = textLength + startPos;
}
if(endPos < 0){
endPos = textLength + endPos;
}
if(textDom.createTextRange){
// IE Support
var range = textDom.createTextRange();
range.moveStart("character",-textLength);
range.moveEnd("character",-textLength);
range.moveStart("character", startPos);
range.moveEnd("character",endPos);
range.select();
}else{
// Firefox support
textDom.setSelectionRange(startPos, endPos);
textDom.focus();
}
}
}

五. 在光标后插入文本：

/**
* 在光标后插入文本
* 参数：
*     textDom  [JavaScript DOM String] 当前对象
*     value  [String]  要插入的文本
*/
function insertAfterText(textDom, value) {
var selectRange;
if (document.selection) {
// IE Support
textDom.focus();
selectRange = document.selection.createRange();
selectRange.text = value;
textDom.focus();
}else if (textDom.selectionStart || textDom.selectionStart == '0') {
// Firefox support
var startPos = textDom.selectionStart;
var endPos = textDom.selectionEnd;
var scrollTop = textDom.scrollTop;
textDom.value = textDom.value.substring(0, startPos) + value + textDom.value.substring(endPos, textDom.value.length);
textDom.focus();
textDom.selectionStart = startPos + value.length;
textDom.selectionEnd = startPos + value.length;
textDom.scrollTop = scrollTop;
}
else {
textDom.value += value;
textDom.focus();
}
}