判断字符串sContent是否以指定的后缀sEnd结尾

function endWith(sContent, sEnd) {
    var endReg = new RegExp(".*(?<=" + sEnd + ")$", "i");
    return endReg.test(sContent);
}
console.log(endWith("abcsdfffabc", "abc"));   // true

判断字符串sContent是否以指定的前缀sStart开头

function startWith(sContent, sStart) {
    var startReg = new RegExp("^(?=" + sStart + ").*", "i");
    return startReg.test(sContent);
}
console.log(startWith("abcffdfabc", "abc"));   // true

判断字符串出现的次数

function sCount(sContent, sMatch) {
    var matchReg = new RegExp(sMatch, "ig");
    return sContent.match(matchReg) ? sContent.match(matchReg).length : 0;
}
console.log(sCount("asdffdabcsfabffabc", "abc"));

手机号掩码函数

function encryptPhoneNumber(phoneNumber) {
  return phoneNumber.replace(/(\d{3})(\d{4})(\d{4})/, '$1****$3')
}

几个 ? 元字符用法

(?:str)   非捕获组

(?=str)   肯定式向前查找

(?!str)   否定式向前查找

(?<=str)  肯定式向后查找

(?<!str)  否定式向后查找