The js validation string function example code is as follows:

// Remove spaces
function jsTrim(value) {
  var reg = /^\S$/;
  if (!value) return "";
  if (value.length == 0)
    return value;
  else {
    var lp, rp;
    lp = 0; rp = value.length - 1;
    while ((value.charAt(lp) == " " || (value.charCodeAt(lp) < 128 ? (reg.test(value.charAt(lp)) == false ? true : false) : false) || value.charAt(rp) == " " || (value.charCodeAt(rp) < 128 ? (reg.test(value.charAt(rp)) == false ? true : false) : false)) && rp >= lp) {
      if (value.charAt(lp) == " " || value.charCodeAt(lp) < 128 ? (reg.test(value.charAt(lp)) == false ? true : false) : false)
        lp++;
      if (value.charAt(rp) == " " || value.charCodeAt(rp) < 128 ? (reg.test(value.charAt(rp)) == false ? true : false) : false)
        rp--;
    }
    if (lp > rp)
      return "";
    else
      return (value.substring(lp, rp + 1));
  }
}
// String length
function strlength(s) {
  var s_length = s.length;
  return s_length;
}
// Mobile phone number verification function
String.prototype.Trim = function() {
  var m = this.match(/^\s*(\S+(\s+\S+)*)\s*$/);
  return (m == null) ? "" : m[1];
}
String.prototype.isMobile = function() {
  return (/^(?:13\d|15\d|18\d|19\d|17\d|14\d)-?\d{5}(\d{3}|\*{3})$/.test(this.Trim()));
}
//* Identify whether the telephone number and mobile phone number are valid
//* Return  true:false
//*/
function checkPhone(phone)
{
// Verify phone number mobile phone number, including 153 , 159 Segment number
if (phone==""){
alert(" Phone number cannot be empty! ");
return false;
}
if (phone != ""){
var p1 = /^(([0\+]\d{2,3}-)?(0\d{2,3})-)?(\d{7,8})(-(\d{3,}))?$/;
var me = false;
if (p1.test(phone)) me=true;
if (!me){
//alert(' Sorry, there is an error in the telephone number you entered. Please use between area code and telephone number - Segmentation ');
return false;
}
}
return true;
}
// Mailbox address validation function
function checkmail(mail) {
//  var strr;
//  re = /(\w+@\w+\.\w+)(\.{0,1}\w*)(\.{0,1}\w*)/i;
//  re.exec(mail);
//  if (RegExp.$3 != "" && RegExp.$3 != "." && RegExp.$2 != ".")
//    strr = RegExp.$1 + RegExp.$2 + RegExp.$3
//  else {
//    if (RegExp.$2 != "" && RegExp.$2 != ".")
//      strr = RegExp.$1 + RegExp.$2
//    else
//      strr = RegExp.$1
//  }
//  if (strr != mail) { return false } else { return true }
  //  return true;
  var remail = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
  return mail.match(remail);
}
// Judgement number
function CheckNumber(n) {
  var checkOK = "0123456789-.";
  var allValid = true;
  var decPoints = 0;
  var allNum = "";
  for (i = 0; i < n.length; i++) {
    ch = n.charAt(i);
    for (j = 0; j < checkOK.length; j++)
      if (ch == checkOK.charAt(j))
      break;
    if (j == checkOK.length) {
      allValid = false;
      break;
    }
    if (ch == ".") {
      allNum += ".";
      decPoints++;
    }
    else
      allNum += ch;
  }
  if (!allValid)
    return false;
  if (decPoints > 1)
    return false;
  return true;
}
// Judgement number
function CheckN(n) {
  var checkOK = "0123456789";
  var allValid = true;
  var decPoints = 0;
  var allNum = "";
  for (i = 0; i < n.length; i++) {
    ch = n.charAt(i);
    for (j = 0; j < checkOK.length; j++)
      if (ch == checkOK.charAt(j))
      break;
    if (j == checkOK.length) {
      allValid = false;
      break;
    }
    if (ch == ".") {
      allNum += ".";
      decPoints++;
    }
    else
      allNum += ch;
  }
  if (!allValid)
    return false;
  if (decPoints > 1)
    return false;
  return true;
}
var g_MINY = 1601;
var g_MAXY = 4500;
var rgMC = new Array(12);
rgMC[0] = 31; rgMC[1] = 28; rgMC[2] = 31; rgMC[3] = 30; rgMC[4] = 31; rgMC[5] = 30; rgMC[6] = 31; rgMC[7] = 31; rgMC[8] = 30; rgMC[9] = 31; rgMC[10] = 30; rgMC[11] = 31;
function isdigit(c) {
  return (c >= '0' && c <= '9');
}
function GetMonthCount(m, y) {
  var c = rgMC[m - 1];
  if ((2 == m) && IsLeapYear(y)) c++;
  return c;
}
function atoi(s) {
  var t = 0;
  for (var i = 0; i < s.length; i++) {
    var c = s.charAt(i);
    if (!isdigit(c)) return t;
    else t = t * 10 + (c - '0');
  }
  return t;
}
// Judgment date
function CheckDate(t) {
  var l = t.length;
  if (0 == l) return false;
  var cSp = '\0';
  var sSp1 = '';
  var sSp2 = '';
  for (var i = 0; i < t.length; i++) {
    var c = t.charAt(i);
    if (c == ' ' || isdigit(c)) continue;
    else if (cSp == '\0' && (c == '/' || c == '-' || c == '.')) {
      cSp = c;
      sSp1 = t.substring(i + 1, l);
    }
    else if (c == cSp) sSp2 = t.substring(i + 1, l);
    else if (c != cSp) return false;
  }
  if (0 == sSp1.length) return false;
  var m;
  var d;
  var y;
  if (0 == sSp2.length) return false;
  m = atoi(sSp1);
  d = atoi(sSp2);
  y = atoi(t);
  if (y < 100) {
    y = 1900 + y;
    while (y < g_yLow) y = y + 100;
  }
  if (y < g_MINY || y > g_MAXY || m < 1 || m > 12) return false;
  if (d < 1 || d > GetMonthCount(m, y)) return false;
  g_month = m;
  g_day = d;
  g_year = y;
  return true;
}
// Validation string must be a combination of numeric letters
function isNumAndStr(elem){
    var str = elem.value;
   var regexpUperStr=/[A-Z]+/;
   var reexpLowerStr=/[a-z]+/;
   var regexpNum=/\d+/;
   var uperStrFlag = regexpUperStr.test(str);
   var lowerStrFlag = reexpLowerStr.test(str);
   var numFlag = regexpNum.test(str);
   if((uperStrFlag&&lowerStrFlag)||(lowerStrFlag&&numFlag)||(uperStrFlag&&numFlag))
     return true;
   else
    return false;
}
// Validation string must be a combination of numbers and letters
function checkPSW(str) {
  if (str != "") {
    var p1 = /(?!^[0-9]*$)(?!^[a-zA-Z]*$)^([a-zA-Z0-9]{2,})$/;
    var me = false;
    if (p1.test(str)) me = true;
    if (!me) {
      return false;
    }
  }
  return true;
}
// Validation string must be a combination of numbers and letters
function checklen(str) {
  if (str.length < 8 ) {
      return false;
    }
  return true;
}
// Unit price
function ISprice(v) {
  var Mreg = /^[0-9]{1,10}(\.[0-9]{1,3})?$/;
  if (Mreg.test(v)) {
    return true;
  }
  else {
    return false;
  }
}