如何检查我是否在 javascript 中提交了空白输入？我写了一个程序，但它不工作

Question

我使用脚本标签在 HTML 文件中编写了 javascript 代码，我想知道我的输入是大于还是小于 10 或等于 10 或任何空白输入。我用if-else方法解决这个问题，但我的最后一个 else if 条件是“你的输入是空白”不以任何方式输出。

//f1 function will run when some hit the submit button
function f1() {
  //here we are taking the value of the input field using id "myinput" in the variable called myinputvar
  var myinputvar = document.getElementById("myinput").value;
  if (myinputvar > 10) {
    document.getElementById("txt").innerHTML = "Your input number is greater than 10";
  } else if (myinputvar < 10) {
    document.getElementById("txt").innerHTML = "Your input number is less than 10";
  } else if (myinputvar = 10) {
    document.getElementById("txt").innerHTML = "Your input number is 10";
  } else if (myinputvar = " ") {
    document.getElementById("txt").innerHTML = "Your input is blank";
  }
}

<!-- this is the input tag to take inputs from user -->
Enter a integer number between 0 to anynumber = <input type="text" id="myinput"><br><br>
<!-- this is the button to submit the value -->
<button onclick="f1()">submit</button>
<!-- this is the heading tag to print the output -->
<h1 id="txt"></h1>

Answer 1

仅检查空格输入的通用方法是使用正则表达式模式 ^\s*$。示例代码：

if (/^\s*$/.test(inputvar)) {
    document.getElementById("txt").innerHTML = "Your input is blank";
}

Answer 2

包装在表格中并使其成为必需的

也转换为数字

document.getElementById("myForm").addEventListener("submit", function(e) {
  e.preventDefault(); // stop submission
  //here we are taking the value of the input field using id "myinput" in the variable called myinputvar
  var myinputvar = +document.getElementById("myinput").value; // make it a number
  if (myinputvar > 10) {
    document.getElementById("txt").innerHTML = "Your input number is greater than 10";
  } else if (myinputvar < 10) {
    document.getElementById("txt").innerHTML = "Your input number is less than 10";
  } else if (myinputvar = 10) {
    document.getElementById("txt").innerHTML = "Your input number is 10";
  } else if (myinputvar = " ") {
    document.getElementById("txt").innerHTML = "Your input is blank";
  }
})

<form id="myForm">
  Enter a integer number between 0 to anynumber =
  <input type="text" required id="myinput"><br><br>
  <button>submit</button>
</form>
<h1 id="txt"></h1>

Answer 3

注意不要使用快捷方式：

if (inputvar) {
    // this won't catch "0"!
}

不过更合适

if (inputvar === "") {
    // is empty
}

当然，如果您想将数字作为输入处理，您应该首先检查此条件。

Answer 4

检查给定的输入值是否为有效数字

    function isNumber(n){ return /^-?[\d.]+(?:e-?\d+)?$/.test(n); }

Answer 5

正如 Tim Biegeleisen 提到的，它是这样工作的：

var myinputvar = document.getElementById("myinput").value;
if (/^\s*$/.test(myinputvar)) {
   document.getElementById("txt").innerHTML = "Your input is blank";
} else {
  if (myinputvar > 10) {
     document.getElementById("txt").innerHTML = "Your input number is greater than 10";
  } else if (myinputvar < 10) {
    document.getElementById("txt").innerHTML = "Your input number is less than 10";
  } else if (myinputvar = 10) {
    document.getElementById("txt").innerHTML = "Your input number is 10";
  }
}

Answer 6

您可以使用 ASCII 码来检查

else if(myinputvar.carCodeAt(0) === 13) {
    document.getElementById("txt").innerHTML = "Your input is blank";
}

13为回车键的ASCII码 https://www.asciitable.com/

Answer 7

> This method is also working, the logic is i should have use a nested
> if like this

 
function f1() {
            var myinputvar = document.getElementById("myinput").value;
            if (myinputvar == "") {
                document.getElementById("txt").innerHTML = "Your input is blank";
            } else {
                if (myinputvar > 10) {
                    document.getElementById("txt").innerHTML = "Your input number is greater than 10";
                } else if (myinputvar < 10) {
                    document.getElementById("txt").innerHTML = "Your input number is less than 10";
                } else if (myinputvar = 10) {
                    document.getElementById("txt").innerHTML = "Your input number is 10";
                }
            }

        }

如何检查我是否在 javascript 中提交了空白输入？我写了一个程序，但它不工作

How to check whether i submit blank input in javascript? i have written a program but it is not working

javascript

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