JS判断表单输入是否为空

//去掉输入字符串两边的空格function trim(s) {var count = s.length;var st = 0; // startvar end = count-1; // endif (s == ) return s;while (st < count) {if (s.charAt(st) == )st ++;elsebreak;}while (end st) {if (s.charAt(end) == )end --;elsebreak;}return s.substring(st,end + 1);}假如表单是这样的：<form action=testnew.html name=form1username: <input type=text name=namepassword: <input type=password name=pwd<input type=button name=button value=提交 onclick=isEmpty()</formusername:password:则判断输入是否为空可以这样定义函数：function isEmpty(){//form1是form中的name属性var _form = document.form1;if(trim(_form.name.value)==){alert(用户名不能为空!);return false;}if(trim(_form.pwd.value)==){alert(密码不能为空!);return false;}在表单的按钮处则这样引用：

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