尝试

 var alphabets26 ='abcdefghijklmnopqrstuvwxyz'; 
 var input = prompt（）; 
 input = input.toLowerCase（）; 
 var icount = 0; 
 for（var i = 0; i< alphabets26.length; i ++）{
 var letter = alphabets26 [i]; 
 if（input.indexOf（letter）> -1）
 icount ++; 
} 
 if（icount == 26）
 alert（'所有字母至少找到一次'）; 

其他
警报（'少数字母丢失'）; 

演示： - JSFiddle [ ^ ]

你可以轻松实现自己，例如

  var  exists = []; 

 var  s =   abcdefoo跨度>;  //  输入字符串 


 for （ var  i =  0 ; i <  s.length; ++ i）
 {
 exists [s [i]] =  1 ; 
} 


 for （ var  i =  97 ; i< =  122 ; ++ i） / /  遍历所有小写字符 
 {
c =  String 。 fromCharCode（ⅰ）; 
 if （！exists [c]）
 {
 alert（c +   缺少）; 
 break ; 
} 
} 

还有一个解决方案

 var Your_String =abcdefghijklmnopqrstuvwxyz ; 
 var Result = Your_String.replace（''，''）。split（''）。filter（function（item，i，ar）{return ar.indexOf（item）=== i;}）。加入（''）; 
 document.writeln（Result.length == 26？全部使用：有些遗失）; 

利用：javascript - 仅在字符串中显示一次唯一字符 - Stack Overflow [ ^ ]

Hi, I'm quite new to programming and started with JavaScript.
I'm curious if there is a method to check if a variable has all letters of the alphabet at least once.

What I have tried:

So I have the variable

var string = prompt("Type in message","");

Curious how to check if the message typed in has every letter a to z. if yes alert("All letters found at least once")

try

var alphabets26 = 'abcdefghijklmnopqrstuvwxyz';
       var input = prompt();
       input = input.toLowerCase();
       var icount = 0;
       for (var i = 0; i < alphabets26.length; i++) {
           var letter = alphabets26[i];
           if (input.indexOf(letter) > -1)
               icount++;
       }
       if (icount == 26)
           alert('All letters found at least once');

       else
           alert('Few letters missing');

Demo : - JSFiddle[^]

You can easily implement yourself, for instance

var exists =  [];

var s = "abcdefoo"; // the input string


for (var i=0; i < s.length; ++i)
{
  exists[s[i]] = 1;
}


for ( var i = 97; i<=122; ++i) // loop over all lowercase characters
{
  c = String.fromCharCode(i);
  if ( !exists[c])
  {
    alert(  c + " is missing");
    break;
  }
}

One more solution

var Your_String= "abcdefghijklmnopqrstuvwxyz";
var Result = Your_String.replace(' ','').split('').filter(function(item, i, ar){ return ar.indexOf(item) === i; }).join('');
document.writeln(Result.length == 26 ? "All used" : "Some missing");

Made use of : javascript - Showing unique characters in a string only once - Stack Overflow[^]