仅限字母字符的输入框

Question

  // input intials box
  var createInput = document.createElement("input");
  createInput.setAttribute("type", "text");
  createInput.setAttribute("id", "initials");
  // Max character length of 4 for people who have 2 middle names
  createInput.setAttribute("maxlength", "4");
  // Placeholder text
  createInput.setAttribute("value", "ABC");
  createInput.setAttribute("onkeydown", "return alphaOnly(event);");
  // Input my initials JMS is value is blank
  createInput.setAttribute(
    "onblur",
    "if (this.value == '') {this.value = 'JMS';}"
  );
  // Clear placeholder text onClick
  createInput.setAttribute(
    "onfocus",
    "if (this.value == 'ABC') {this.value = '';}"
  );

  createInput.textContent = "";

  questionsDiv.appendChild(createInput);

  function alphaOnly(event) {
    var key = event.keyCode;
    return (key >= 65 && key <= 90) || key == 8;
  }

因此，我使用 JavaScript 创建了一个只接受首字母的输入。输入框加载并且工作正常，但我的功能没有将键限制为 65-90 + 8，因为错误提示 alphaOnly 未定义。我错过了什么？

Answer 1

这将只使用字母

createInput.setAttribute(
    "onkeypress",
    "return ((event.charCode >= 65 && event.charCode <= 90) || (event.charCode >= 97 && event.charCode <= 122) || (event.charCode == 32))"
  );

这限制了字符

  createInput.setAttribute("maxlength", "4");

仅限字母字符的输入框

Input box for Alpha Characters only

javascript

input

function

keycode

undefined-behavior