JS经常使用例子

// 是否为空，非空返回真，不非为空返回假
function isBlank(str) {
 var blankFlag = true;
 if (str.length == 0) return true;
 for (var i = 0; i < str.length; i++) {
  if ((str.charAt(i) != "") && (str.charAt(i) != " ")) {
   blankFlag = false;
   break;
  }
 }
 return blankFlag;
}

function checkNotNull(theField, fieldName) {
 
 if(isBlank(theField.value)){
  alert(fieldName + "不可为空！");
  theField.focus();
  return false;
 }

 return true;
}

// 是否为数字
function checkNumber(theField, fieldName) {
  var pattern = /^([0-9]|(-[0-9]))[0-9]*((.[0-9]+)|([0-9]*))$/;

  if(theField.value == "") return true;
  if (!pattern.test(theField.value)) {
   alert(fieldName + "必须为合法数字");
   theField.focus();
   theField.select();
   return false;
  }

 return true;
}

// 是否为指定范围数字
function checkNumberRange(theField, fieldName, min, max) {
 if(theField.value == "") return true;
 if (!checkNumber(theField, fieldName)) return false;

 if ((min != "") && (theField.value < min)) {
  alert(fieldName + "不可小于" + min + "！");
  theField.focus();
  theField.select();
  return false;
 }

 if ((max != "") && (theField.value > max)) {
  alert(fieldName + "不可超过" + max + "！");
  theField.focus();
  theField.select();
  return false;
 }

 return true;
}

// 是否为整数
function checkInteger(theField, fieldName) {
 var pattern = /^(d|(-d))d*$/;

 if(theField.value == "") return true;
 if (!pattern.test(theField.value)) {
  alert(fieldName + "必须为整数！");
  theField.focus();
  theField.select();
  return false;
 }

 return true;
}

// 是否为指定范围内整数
function checkIntegerRange(theField, fieldName, min, max) {
 if(theField.value == "") return true;
 if (!checkInteger(theField, fieldName)) return false;

 if ((min != "") && (theField.value < min)) {
  alert(fieldName + "不可小于" + min + "！");
  theField.focus();
  theField.select();
  return false;
 }

 if ((max != "") && (theField.value > max)) {
  alert(fieldName + "不可超过" + max + "！");
  theField.focus();
  theField.select();
  return false;
 }

 return true;
}

// 是否为正数
function checkPositiveNumber(theField, fieldName) {
 if(theField.value == "") return true;
 if (theField.value.charAt(0) == '-') {
  alert(fieldName + "必须为正数！");
  theField.focus();
  return false;
 }

 return true;
}

// 限制字串最大长度
function checkLength(theField, fieldName, maxLength) {
 if(theField.value == "") return true;
 if (theField.value.length > maxLength) {
  alert(fieldName + "的字数最多为" + maxLength + "字！");
  theField.select();
  theField.focus();
  return false;
 }

 return true;
}

// 限制字串长度,注意参数顺序
function checkLength2(theField, fieldName, maxLength, minLength) {
 if(theField.value == "") return true;
 if (theField.value.length > maxLength) {
  alert(fieldName + "的字数最多为" + maxLength + "字！");
  theField.focus();
  return false;
 }

 if ((minLength != "") && (theField.value.length < minLength)) {
  alert(fieldName + "的字数最少为" + minLength + "字！");
  theField.focus();
  return false;
 }

 return true;
}

// 所输入字符串是否均为合法字符
// charBag中为包含全部合法字符的字符串
function checkStrLegal(theField, fieldName, charBag) {
 if(theField.value == "") return true;
    for (var i = 0; i < theField.value.length; i++) {
        var c = theField.value.charAt(i);
        if (charBag.indexOf(c) == -1) {
       alert(fieldName + "含有非法字符(" + c + ")！");
       theField.focus();
       return false;
        }
    }

    return true;
}

// 所输入字符串是否均为合法字符
// charBag中为包含非法字符的字符串
function checkStrLegal2(theField, fieldName, charBag) {
 if(theField.value == "") return true;
    for (var i = 0; i < theField.value.length; i++) {
        var c = theField.value.charAt(i);
        if (charBag.indexOf(c) > -1) {
       alert(fieldName + "含有非法字符(" + c +")！");
       theField.focus();
       return false;
        }
    }

    return true;
}

// 电子邮件验证
function checkEmail(theField) {
 var pattern = /^.+@.+..+$/;

 if(theField.value == "") return true;
 if (!pattern.test(theField.value)) {
  alert("请输入合法的电子邮件地址");
  theField.focus();
  theField.select();
  return false;
 }

 return true;
}

// 弹出一个窗口, 使用系统默认弹开位置 function popWindow(url, width, height, title){     window.open(url,"_blank","toolbar=no,location=no,directories=no, status=no,menubar=no,scrollbars=yes,resizable=yes,width="+width+ ",height="+height+",title="+title); }