jquery可获取文本框最初光标停留位置插件

使用方法

(function($) {
  function focus(target) {
    if (!document.activeElement || document.activeElement !== target) {
      target.focus();
    }
  }

  $.fn.caret = function(pos) {
    var target = this[0];
    var isContentEditable = target && target.contentEditable === 'true';
    if (arguments.length == 0) {
      //get
      if (target) {
        //HTML5
        if (window.getSelection) {
          //contenteditable
          if (isContentEditable) {
            focus(target);
            var selection = window.getSelection();
            // Opera 12 check
            if (!selection.rangeCount) {
              return 0;
            }
            var range1 = selection.getRangeAt(0),
                range2 = range1.cloneRange();
            range2.selectNodeContents(target);
            range2.setEnd(range1.endContainer, range1.endOffset);
            return range2.toString().length;
          }
          //textarea
          return target.selectionStart;
        }
        //IE<9
        if (document.selection) {
          focus(target);
          //contenteditable
          if (isContentEditable) {
              var range1 = document.selection.createRange(),
                  range2 = document.body.createTextRange();
              range2.moveToElementText(target);
              range2.setEndPoint('EndToEnd', range1);
              return range2.text.length;
          }
          //textarea
          var pos = 0,
              range = target.createTextRange(),
              range2 = document.selection.createRange().duplicate(),
              bookmark = range2.getBookmark();
          range.moveToBookmark(bookmark);
          while (range.moveStart('character', -1) !== 0) pos++;
          return pos;
        }
        // Addition for jsdom support
        if (target.selectionStart)
          return target.selectionStart;
      }
      //not supported
      return;
    }
    //set
    if (target) {
      if (pos == -1)
        pos = this[isContentEditable? 'text' : 'val']().length;
      //HTML5
      if (window.getSelection) {
        //contenteditable
        if (isContentEditable) {
          focus(target);
          window.getSelection().collapse(target.firstChild, pos);
        }
        //textarea
        else
          target.setSelectionRange(pos, pos);
      }
      //IE<9
      else if (document.body.createTextRange) {
        if (isContentEditable) {
          var range = document.body.createTextRange();
          range.moveToElementText(target);
          range.moveStart('character', pos);
          range.collapse(true);
          range.select();
        } else {
          var range = target.createTextRange();
          range.move('character', pos);
          range.select();
        }
      }
      if (!isContentEditable)
        focus(target);
    }
    return this;
  }
})(jQuery);