Javascript：如何使用循环功能在一个警报框中显示所有用户输入？

Question

I'm trying to write a function that will show an Alert Box for all the data entered by the user in the form. I must do it only in simple javascript (sorry no jQuery ). My HTML is as follows:

 <form method="POST">
   <label class="form">Name: </label><input type="text" name="name" id="name"><br>
   <label class="form">Address: </label><input type="text" name="address" id="address"><br>
   <label class="form">Email: </label><input type="text" name="email" id="email"><br>

   <button id="submit" type="submit" value="submit" onclick="showAlert()">
   Submit
   </button>
 </form>

My javascript:

 function showAlert() {
     var userInputs = document.getElementsByTagName("input");

     for (var i=0; i < userInputs.length; i++) {
        alert(userInputs.value + " ");
        //Basically my idea would be to implement a loop for as many input fields, 
        //run through all of them, then display ONE SINGLE alert box containing all the 
        //data entered by the user.  But I'm having trouble with how to implement the loop.
    }
 }

How do I implement the loop?

I have written another function that achieves the same effect but it involved writing a long, tedious list of variables for each input field and I don't want to do that since it's messy:

 function alternateShowAlert() {
      var name = document.getElementById('name').value;
      var address = document.getElementById('address').value;
      var email = document.getElementById('email'.value;

      alert(name + " " + address + " " + email)

      //This function, although it works fine, will be too long and tedious if I have 
      //more input fields such as age, city, state, country, gender, etc.  I want to put 
      //it in a loop format but how do I do this?
 }

Answer 1

You have the logic: you need the loop to collect all info, but should show only one alert, so instead of alert'ing inside the loop, you need to do it after:

function showAlert() {
     var userInputs = document.getElementsByTagName("input");
     var infos = ""; // Create a string for the content
     for (var i=0; i < userInputs.length; i++) {
        infos += userInputs[i].value + " "; // Add the info from user input
    }
    alert(infos); // Show one alert at the end
 }

Answer 2

function showAlert() {
  var userInputs = document.getElementsByTagName("input");
  var alertBody = "";
  for (var i=0; i < userInputs.length; i++) {
    alertBody += userInputs[i].value + " ";
  }
  alert(alertBody);                                                                                                                                            
}

document.getElementsByTagName() returns an array, so you need to access the elements of the array using their index: userInputs[i] .

Or you can use Array.prototype.forEach . See the example below.

function showAlert() {
  var userInputs = document.getElementsByTagName("input");
  var alertBody = "";
    Array.prototype.forEach.call(userInputs, function(element) {
      alertBody += element.value + " ";
    });
  alert(alertBody);                                                                                                                                            
}

Answer 3

Martin is getting you part of the way there, but I think you'll trip up at getting the values. Document.getElementsByTagName returns an HTML collection best treated as an array.

So user inputs.value would probably need to be something like userinputs[i].value for Martin's code to work

Answer 4

You can do it in one single line, without any loop:

 function Show() { alert([].slice.call(document.querySelectorAll("input[type='text']")).map(function(x) { return x.id + ": " + x.value; }).join("\\n")); } 

 Name: <input type="text" id="name" /><br /> Address: <input type="text" id="address" /><br /> Email: <input type="text" id="email" /><br /> <button type="button" onclick="Show();">Show</button> 

The method querySelectorAll is supported by all modern browsers (IE 9+) and is the plain JS equivalent to jQuery selectors. However, it returns a node list which should be converted to plain array in order for us to use the desired .map() method to get all the values easily.