To choose the specific characters of the content which included in the specific component.

selectText

	/**
	 * To choose the specific characters of the content which included in the specific component.
	 * @param {String} tagName: the name of a tag(eg.textarea,input etc.)
	 * @param {Object} obj: component
	 * @param {Integer} begin: the start index
	 * @param {Integer} end: the end index.
	 * @author wangmeng
	 * @date 2011-10-10
	 */
	function selectText(tagName, obj, begin, end){
		if(document.selection){
			if(obj.tagName == tagName){
				var i = obj.value.indexOf("\r", 0);
				while(i != -1 && i < end){
					end--;
					if(i < begin){
						begin --;
					}
					i = obj.value.indexOf("\r", i+1);
				}
			}
			var range = obj.createTextRange();
			range.collapse(true);
			range.moveStart('character', begin);
			if(end != undefined){
				range.moveEnd('character', end-begin);
			}
			range.select();
		}else{
			obj.selectionStart = begin;
			var sel_end = (end == undefined) ? begin : end;
			obj.selectionEnd = Math.min(sel_end, obj.value.length);
			obj.focus();
		}