javascript 使用户输入数字并且不允许他们输入空白输入

rdlzhqv9 于 2023-05-21 发布在 Java

关注(0)|答案(2)|浏览(125)

我正在做一个javascript程序，程序会问用户是想计算距离、速度还是时间。该计划的工作，但我希望能够使它的地方，用户不能输入一个空白的输入，以及不允许程序继续，如果他们的输入不是一个数字（在数字是必要的）
//这个程序要求用户输入他们是否想计算距离、时间或速度。//根据他们的答案，他们被要求输入其他两个选项的值//然后程序计算速度，距离或时间

function calculate(){
try{
    let question = prompt("Would you like to calculate Distance(km), Time(h) or Speed(kph)");
    let answer = question.toLowerCase();
        if(answer === "distance" && answer != ""){
            let time = Number(prompt("Please enter your time in hours:"));
            let speed = Number(prompt("Please enter your speed:"));
            let calculation = speed * time;
            console.log(`The Distance is: ${calculation} km`);
        }else if(answer === "time" && answer != ""){
            let distance = Number(prompt("Please enter your distance:"));
            speed = Number(prompt("Please enter your speed:"));
            let calculation2 = distance / speed;
            console.log(`Your Time is: ${calculation2} hours`);
        }else if(answer === "speed" && answer != ""){
            distance = Number(prompt("Please enter your distance:"));
            time = Number(prompt("Please enter your time in hours:"));
            calculation3 = distance / time;
            console.log(`Your speed is: ${calculation3} kph`)
        }else{
          calculate();
        }
}catch(e){
calculate();
}
}

let output = calculate();

JavaScript

来源：https://stackoverflow.com/questions/76262748/making-a-user-input-a-number-and-not-allowing-them-to-input-a-blank-input

2条答案

按热度按时间

643ylb081#

let 
  time,
  speed,
  calculation;

time = Number(prompt("Please enter your time in hours:"));

if(!time) {
  time = Number(prompt("Please enter your time in hours:"));
}

speed = Number(prompt("Please enter your speed:"));

if(!speed) {
  speed = Number(prompt("Please enter your speed:"));
}

您可以在提示前加上+来替换数字。time = +(prompt("Please enter your time in hours:"));
如果你想要一个更快，更清晰的想法，你可以使用ternary operator
基本上就是一个简短的if-else

time = !time ? +(prompt("Please enter your time in hours:")); : time;

赞(0）回复(0）举报 2023-05-21

ki1q1bka2#

您可以尝试分离功能并编写一个泛型函数，该函数递归地调用自身，直到给出有效的输入。
可能的实现之一：

function getTypePrompt() {
    const question = prompt("Would you like to calculate Distance(km), Time(h) or Speed(kph)");
    if (question === "") {
        return getTypePrompt();
    }

    if (question === null) {
        return null;
    }

    switch (question) {
        case "distance":
        case "time":
        case "speed":
            return question;
    }

    return getTypePrompt();
}

function getNumberPrompt(message) {
    const response = prompt(message);
    if ((response == null) || (response === "")) {
        return getNumberPrompt(message);
    }

    const data = parseInt(response);

    if (!isNaN(data)) {
        return data;
    }

    return getNumberPrompt(message);
}


try {
    let question = getTypePrompt();
    let answer = question.toLowerCase();
    if (answer === "distance") {
        let time = getNumberPrompt("Please enter your time in hours:");
        let speed = getNumberPrompt("Please enter your speed:");
        let calculation = speed * time;
        document.write(`The Distance is: ${calculation} km`);
    } else if (answer === "time") {
        let distance = getNumberPrompt("Please enter your distance:");
        speed = getNumberPrompt("Please enter your speed:");
        let calculation2 = distance / speed;
        document.write(`Your Time is: ${calculation2} hours`);
    } else if (answer === "speed") {
        distance = getNumberPrompt("Please enter your distance:");
        time = getNumberPrompt("Please enter your time in hours:");
        calculation3 = distance / time;
        document.write(`Your speed is: ${calculation3} kph`)
    } else {
        document.write("You have cancelled the calculation");
    }
} catch (e) {
    document.write("Something went wrong!");
}

赞(0）回复(0）举报 2023-05-21

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javascript 使用户输入数字并且不允许他们输入空白输入

2条答案

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