设置输入框的光标位置

function setCaret(el,start,end){
		el.focus();
		if(start === true){
			start = el.value.length;
		}
		if(typeof end === 'undefined'){
			end = start;
		}else if(end === true){
			end = el.value.length;
		}
		start = Math.max(0,start);
		end = Math.min(end,el.value.length);
		if ("setSelectionRange" in el) { 
			//Chrome/Firefox/IE9+/Safari3+/Opera8+
            el.setSelectionRange(start, end);
        }else{
        	//IE6~8
        	var userRange = document.selection.createRange();
        	userRange.moveStart("character",start);
        	userRange.moveEnd("character",end);
        	userRange.select();
        }
}


//usage: 
var i = document.getElementById('inputBox');
setCaret(i,0);//开始
setCaret(i,true);//结束

setCaret(i,1,5);//选中1~5个字符

setCaret(i,0,true);//选中所有值