javascript - 如何在表单上使用 "sticky"电话号码格式占位符？

Question

我想在表单中显示电话号码的格式作为占位符，而不是在用户键入号码时被删除。

html 占位符随着用户键入而消失。我希望占位符保留并引导用户键入电话号码。

<form action="payonline.html">
     <input type="tel" id="phone" name="phone" pattern="[0-9]{3}-[0-9]{3}-[0-9]{4}" required placeholder="___ - ___ - ____ ">                             
       <input type="submit" value="Submit">
  </form>

Answer 1

我认为您需要在 javascript 中使用 onkeypress 和 onkeyup 事件来创建更加用户友好的电话输入。 您可以使用下面的代码。我不确定您使用的是 jquery，所以我使用纯 javascript。

<form action="payonline.html">
     <input type="tel" id="phone" name="phone" pattern="[0-9]{3}-[0-9]{3}-[0-9]{4}" required placeholder="___ - ___ - ____ " onkeypress="validate_int(this)" onkeyup="phone_number_mask()">                             
       <input type="submit" value="Submit">
  </form>
<script>

 function validate_int(myEvento) {
  if ((myEvento.charCode >= 48 && myEvento.charCode <= 57) || myEvento.keyCode == 9 || myEvento.keyCode == 10 || myEvento.keyCode == 13 || myEvento.keyCode == 8 || myEvento.keyCode == 116 || myEvento.keyCode == 46 || (myEvento.keyCode <= 40 && myEvento.keyCode >= 37)) {
    dato = true;
  } else {
    dato = false;
  }
  return dato;
}
function phone_number_mask() {
      var myMask = "___-___-____";
      var myCaja = document.getElementById("phone");
      var myText = "";
      var myNumbers = [];
      var myOutPut = ""
      var theLastPos = 1;
      myText = myCaja.value;
      //get numbers
      for (var i = 0; i < myText.length; i++) {
        if (!isNaN(myText.charAt(i)) && myText.charAt(i) != " ") {
          myNumbers.push(myText.charAt(i));
        }
      }
      //write over mask
      for (var j = 0; j < myMask.length; j++) {
        if (myMask.charAt(j) == "_") { //replace "_" by a number 
          if (myNumbers.length == 0)
            myOutPut = myOutPut + myMask.charAt(j);
          else {
            myOutPut = myOutPut + myNumbers.shift();
            theLastPos = j + 1; //set caret position
          }
        } else {
          myOutPut = myOutPut + myMask.charAt(j);
        }
      }
      document.getElementById("phone").value = myOutPut;
      document.getElementById("phone").setSelectionRange(theLastPos, theLastPos);
    }


</script>