如何用javascript生成一个字母

Question

 function myFunction() { var x = document.getElementById("demo"); var alhpabet = ["ABCDEFGHIJKLMNOPQRSTUVWXYZ"]; x.innerHTML = Math.floor((Math.random() * alhpabet.lengthS)); } 

 <button onclick="myFunction()">Try it</button> <p id="demo"></p> 

How can I generate one letter with javascript?

Answer 1

You could try this:

  function myFunction() { var x = document.getElementById("demo"); var min = "A".charCodeAt(0); var max = "Z".charCodeAt(0); var c = String.fromCharCode(Math.floor(Math.random() * (max - min)) + min); x.innerHTML = c; } 

 <button onclick="myFunction()">Try it</button> <p id="demo"></p> 

Answer 2

You should use ASCII . The range for uppercase alphabet letters is from 65-90.

function myFunction() {
    var x = document.getElementById("demo");
    var charCode = Math.floor(Math.random() * (90 - 65 + 1)) + 65;
    x.innerHTML = String.fromCharCode(charCode);
}

Answer 3

You're nearly there.

Your Math.floor function gets a random index , but not the letter. Also, your 'array' wasn't actually an array, you need each letter in quotes, separated by a comma. Alternatively, you can call split on a string but lets ignore that for now.

Once you have the index, you can return the letter found at that index by putting alphabet[index] .

Also, I'm sure you saw the comments but lengthS should be length . And technically alhpabet should be alphabet .

 function myFunction() { var x = document.getElementById("demo"); var alphabet = ["A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"]; var index = Math.floor((Math.random() * alphabet.length)); x.innerHTML = alphabet[index]; } 

 <button onclick="myFunction()">Try it</button> <p id="demo"></p> 

Answer 4

You are almost done. As you have created alphabet variable as an array, you should use the only first alphabet[0] :

 function myFunction() { var x = document.getElementById("demo"), alphabet = ["ABCDEFGHIJKLMNOPQRSTUVWXYZ"], random = Math.floor(Math.random() * alphabet[0].length); x.innerHTML = alphabet[0][random]; } 

 <button onclick="myFunction()">Try it</button> <p id="demo"></p> 

Answer 5

Basically you need a string and not an array with a string inside. Then take length propery for multiplying the random number.

For the result take the random value as index for the string to get a single letter.

 function myFunction() { var x = document.getElementById("demo"), abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; x.innerHTML = abc[Math.floor((Math.random() * abc.length))]; } 

 <button onclick="myFunction()">Try it</button> <p id="demo"></p>