Question

我有一个功能，询问您确定年龄的问题。如果用户输入字符串值或根本没有输入任何内容，我想取消该功能并发出提醒。

到目前为止，这是我的代码：

<button id="btn"> Calculate Age </button>

<p id="para"></p>


document.getElementById("btn").addEventListener("click", ageCalc);


function ageCalc () {

    // Calculate year of birth

    var year = prompt("What year were you born?");
    if (parseInt(year) < 1917) {
        return alert("Please enter a valid year");
    }

    // Calculate month of birth

    var month = prompt("Numerically, what month were you born?");

    if (parseInt(month) > 12 || parseInt(month) < 1 ) {
        return alert("Please enter a valid month!");
    }


    // Calculate day of birth

    var day = prompt("What day were you born?");

    if(parseInt(day) > 32 || parseInt(day) < 1) {
        return alert("Please enter a valid day!");
    }

    // Calculate age based on user input

    var presentDate = new Date ();
    var birthDate = new Date(year,month,day);
    var age = (presentDate - birthDate) / 1000 / 60 / 60 / 24 / 365;

    return document.getElementById("para").innerHTML = "You are " + Math.floor(age) + " years old.";
}

这里的举动是什么？我假设它将以某种方式调整if语句以检查字符串或空白语句，但我有点丢失。有什么想法吗？

Answer 1

您可以通过简单添加if检查来排除null / undefined / empty year值。另外，请始终为parseInt方法添加第二个radix参数：

var year = prompt("What year were you born?");
if (!year || parseInt(year, 10) < 1917) {       
   return alert("Please enter a valid year");
}

您可以对month和day执行相同操作。

Answer 2

    document.getElementById("btn").addEventListener("click", ageCalc);


    function ageCalc () {

// Calculate year of birth

        var year = prompt("What year were you born?");
        if (parseInt(year) < 1917) {
            return alert("Please enter a valid year");
        }
        else if (year == null)
            return;

// Calculate month of birth

        var month = prompt("Numerically, what month were you born?");

        if (parseInt(month) > 12 || parseInt(month) < 1 ) {
            return alert("Please enter a valid month!");
        }
        else if (month == null)
            return;


// Calculate day of birth

        var day = prompt("What day were you born?");

        if(parseInt(day) > 32 || parseInt(day) < 1) {
            return alert("Please enter a valid day!");
        }
        else if (day == null)
            return;

// Calculate age based on user input

        var presentDate = new Date ();
        var birthDate = new Date(year,month,day);
        var age = (presentDate - birthDate) / 1000 / 60 / 60 / 24 / 365;

        return document.getElementById("para").innerHTML = "You are " + Math.floor(age) + " years old.";
    }

Answer 3

使用parseInt()时检查输入是否正确解析，检查其结果是否为NaN，如下所示：

if( parseInt(month) == NaN ){ alert("invalid input"); return false; }

如果用户键入非int可解析输入，它将停止执行。

年龄计算器：检查空白输入或字符串输入

3 个答案: