$(‘input[name="teams"]:checked‘).size()　　

1     // 全选2     $("#quanteam").bind("click", function () {3         $("[name = teams]:checkbox").attr("checked", true);4     });5     // 全不选6     $("#quanteam1").bind("click", function () {7         $("[name = teams]:checkbox").attr("checked", false);8     });

<input type="checkbox" name="" id="quanteam" onClick="this.value=http://www.mamicode.com/check(this.form.teams)"/> 全选

var checkflag = "false";function check(field) {	if (checkflag == "false") {		for (i = 0; i < field.length; i++) {			field[i].checked = true;}			checkflag = "true";	}else {		for (i = 0; i < field.length; i++) {			field[i].checked = false; }			checkflag = "false";	}}