Question

这是我一直在努力的代码。

var storeUsersInfo = [];
var amountOfUsers = prompt("How many users do you want?");
amountOfUsers = parseInt(amountOfUsers);
function returnUserInput() {
    var askFirstName = prompt("What is your first name?");
    var askLastName = prompt("What is your last name" + " " +       titleCase(askFirstName) + "?");
    var askAge = prompt("How old are you" + " " + titleCase(askFirstName) +  " " + titleCase(askLastName) + "?");

        if(askAge != int) {
            alert("Not a valid input")

        };

    return {
        firstName: titleCase(askFirstName),
        lastName: titleCase(askLastName),
        age: askAge
    };
};
function titleCase(string) {
    return string.charAt(0).toUpperCase() + string.slice(1); 
};

for(var i = 0; i < amountOfUsers; i++) {
    storeUsersInfo[i] = returnUserInput();
}
console.log(storeUsersInfo);

我想知道如何检查askAge的输入以查看它是否等于数字。

我尝试了一些代码，你可以在第9-12行看到，我无法弄清楚。我知道它必须用typeof做点什么。

思想？

Answer 1

将它乘以1，如果它返回NaN并且与原始输入不同 - 它不是数字

        var askAge = prompt("How old are you" + " " + titleCase(askFirstName) +  " " + titleCase(askLastName) + "?");
        var askedAge=parseInt(askAge)*1;
          if(askedAge != askAge) {
              alert("Not a valid input");
            }

Answer 2

这可以使用Number.isInteger和Number.parseInt的组合来解决。这两个都已在ES2015标准化。

以下表达式将检查年龄是否有效：

Number.isInteger(Number.parseInt(askAge));

请注意，您必须先将用户输入解析为整数;这可以产生有效的整数，也可以产生NaN。

如果是整数，那么Number.isInteger将表达true;否则，解析的数字为NaN，表达式将变为false。

Answer 3

我想你可以使用这段代码，

function isNumeric(x) {
  return !isNaN(parseFloat(x)) && isFinite(x);
}

Answer 4

您可以使用

Number.isInteger(askAge)

参考： https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isInteger

Answer 5

试试这个

var check = /^[0-9]+$/;
var checkall = askAge.match(check);
if (!checkall){ 
                 alert("Not a valid input")
       }

Answer 6

这个神秘的答案：

var askAge = prompt("How old are you" + " " + titleCase(askFirstName) +  " " + titleCase(askLastName) + "?");
if(!Number.isInteger(Number.parseInt(askAge))) {
    alert("Not a valid input")
};

更多

您的假设部分正确，您必须检查数字的类型以确保它是一个数字，并且它是一个整数。你实际上如何做有几种选择。这是一个应该工作的。

您必须确定是否要使用Number()或Number.parseInt()，因为此处的确定会对可接受的值产生影响。

鉴于此，我选择在此答案中使用parseInt。我还构造它不接受0作为用户数量的值。

首先我们在isInteger中使用或创建parseInt和Number：

Number.isInteger = Number.isInteger || function(value) { return typeof value === "number" && isFinite(value) && Math.floor(value) === value; }; Number.parseInt = Number.parseInt || parseInt;

声明我们的其他功能:(评论）

// this will error out if "Cancel" on the prompt is clicked (null is passed in mystring) function titleCase(mystring) { return mystring.charAt(0).toUpperCase() + mystring.slice(1); } function returnUserInput() { var isValid = false; var askFirstName = ""; var askLastName = ""; var askAge = null; do { askFirstName = prompt("What is your first name?"); // currently accepts " " as a valid name askLastName = prompt("What is your last name" + " " + titleCase(askFirstName) + "?"); // accepts " " as a valid name askAge = prompt("How old are you" + " " + titleCase(askFirstName) + " " + titleCase(askLastName) + "?"); isValid = Number.isInteger(Number.parseInt(askAge)); if (!isValid) { alert("Not a valid input"); } } while (!isValid); // accepts 0 and negative values as age return { firstName: titleCase(askFirstName), lastName: titleCase(askLastName), age: Number.parseInt(askAge) // was using the unparsed string "4' if 4 was entered }; }

使用功能：

var storeUsersInfo = []; var amountOfUsers = 0; var enteredCount = 0; do { amountOfUsers = prompt("How many users do you want?"); enteredCount = Number.parseInt(amountOfUsers, 10);// parse it } while (!(Number.isInteger(Number.parseInt(amountOfUsers, 10))) && !enteredCount > 0) amountOfUsers = enteredCount; for (var i = 0; i < amountOfUsers; i++) { storeUsersInfo[i] = returnUserInput(); } console.log(storeUsersInfo);// console.dir might also work (better?)

如何检查输入是否是js中的数字

6 个答案: