javascript - 检查字符串的第一个字符是否为数字会报错，表明 charat 不是有效方法

Question

我有一个方法可以根据 3 个正则表达式验证字段并根据失败的表达式返回错误。

function mfpValidateValue()
{
    var pCtrl = window.document.forms[0].txtValue;

    var pStrValue  =  mTrim(pCtrl.value);
    if (pStrValue == '')
        return true;

    var regexNum = new RegExp("^[0-9]{9}.{0,3}$"); // First 9 are numeric followed by up to any 3 characters
    var regexLetter1 = new RegExp("^[A-Z]{1,3}[0-9]{6}$"); //Up to the first 3 are alpha, then there are exactly 6 numbers
    var regexLetter2 = new RegExp("^[A-Z]{1,3}[0-9]{9}$"); //Up to the first 3 are alpha, then there are exactly 9 numbers
    var error = "";

    // If any of the RegEx fails, set base error message
    if (!regexNum.test(pStrValue) || !regexLetter1.test(pStrValue) || !regexLetter2.test(pStrValue))
        error = "Please enter a valid Value.";

    // Set more specific error message. 
    if (!isNaN(pStrValue.charat(0)))
        error += " If the first character of Value is a digit, then the first nine characters must be digits.";
    else
        error += " If the first character of Value is a letter, up to the first three characters must be letters proceeded by 6 or 9 digits.";

    return (error == "");
}

我在这一行收到以下错误消息:

    if (!isNaN(pStrValue.charat(0)))

Object doesn't support property or method 'charat'

pStrValue 中的值为:

"12345678"

JavaScript 是否在这里模糊地使用术语“对象”来指代我的特定变量，或者它实际上认为 pStrValue 是一个对象而不是字符串？

Answer 1

你犯了一个小错误。 charat() 不是函数，但 charAt() 是。

你的代码应该是

 if (!isNaN(pStrValue.charAt(0)))

这是函数

http://www.w3schools.com/jsref/jsref_charat.asp