我的文档正文中有一个输入字段，我需要在用户键入时对其进行格式化。它应该在区号周围加上括号，然后在三到四位数字之间加上一个破折号。

例如:(123) 456 - 7890

当用户键入时，它应该类似于:

(12
(123)
(123) 456
(123) 456 - 78
(123) 456 - 7890

最佳答案

新的 ES6 答案

HTML

<input id="phoneNumber" maxlength="16" />

JavaScript (ES6)

const isNumericInput = (event) => {
    const key = event.keyCode;
    return ((key >= 48 && key <= 57) || // Allow number line
        (key >= 96 && key <= 105) // Allow number pad
    );
};

const isModifierKey = (event) => {
    const key = event.keyCode;
    return (event.shiftKey === true || key === 35 || key === 36) || // Allow Shift, Home, End
        (key === 8 || key === 9 || key === 13 || key === 46) || // Allow Backspace, Tab, Enter, Delete
        (key > 36 && key < 41) || // Allow left, up, right, down
        (
            // Allow Ctrl/Command + A,C,V,X,Z
            (event.ctrlKey === true || event.metaKey === true) &&
            (key === 65 || key === 67 || key === 86 || key === 88 || key === 90)
        )
};

const enforceFormat = (event) => {
    // Input must be of a valid number format or a modifier key, and not longer than ten digits
    if(!isNumericInput(event) && !isModifierKey(event)){
        event.preventDefault();
    }
};

const formatToPhone = (event) => {
    if(isModifierKey(event)) {return;}

    const input = event.target.value.replace(/\D/g,'').substring(0,10); // First ten digits of input only
    const areaCode = input.substring(0,3);
    const middle = input.substring(3,6);
    const last = input.substring(6,10);

    if(input.length > 6){event.target.value = `(${areaCode}) ${middle} - ${last}`;}
    else if(input.length > 3){event.target.value = `(${areaCode}) ${middle}`;}
    else if(input.length > 0){event.target.value = `(${areaCode}`;}
};

const inputElement = document.getElementById('phoneNumber');
inputElement.addEventListener('keydown',enforceFormat);
inputElement.addEventListener('keyup',formatToPhone);

如果你想摆弄它:
https://jsfiddle.net/rafj3md0/

免责声明:
值得注意的是，如果您尝试修改数字的中间，这会有点奇怪，因为浏览器在设置元素值后处理插入符号位置的方式。解决这个问题是可行的，但需要比我现在更多的时间，而且有一些图书馆可以处理这样的事情。

旧版 ES5 答案

如果您的 HTML 看起来像:
<input type="text" id="phoneNumber"/>

您的 JavaScript 函数可以是:

// A function to format text to look like a phone number
function phoneFormat(input){
        // Strip all characters from the input except digits
        input = input.replace(/\D/g,'');
        
        // Trim the remaining input to ten characters, to preserve phone number format
        input = input.substring(0,10);

        // Based upon the length of the string, we add formatting as necessary
        var size = input.length;
        if(size == 0){
                input = input;
        }else if(size < 4){
                input = '('+input;
        }else if(size < 7){
                input = '('+input.substring(0,3)+') '+input.substring(3,6);
        }else{
                input = '('+input.substring(0,3)+') '+input.substring(3,6)+' - '+input.substring(6,10);
        }
        return input; 
}

当然，您需要一个事件监听器:

document.getElementById('phoneNumber').addEventListener('keyup',function(evt){
        var phoneNumber = document.getElementById('phoneNumber');
        var charCode = (evt.which) ? evt.which : evt.keyCode;
        phoneNumber.value = phoneFormat(phoneNumber.value);
});

除非您可以将电话号码存储为格式化字符串(我不推荐这样做)，否则您需要在提交值之前清除非数字字符:
document.getElementById('phoneNumber').value.replace(/\D/g,'');

如果您想通过奖励输入过滤查看此操作，请查看此 fiddle :
http://jsfiddle.net/rm9vg16m/

// Format the phone number as the user types it
document.getElementById('phoneNumber').addEventListener('keyup', function(evt) {
  var phoneNumber = document.getElementById('phoneNumber');
  var charCode = (evt.which) ? evt.which : evt.keyCode;
  phoneNumber.value = phoneFormat(phoneNumber.value);
});

// We need to manually format the phone number on page load
document.getElementById('phoneNumber').value = phoneFormat(document.getElementById('phoneNumber').value);

// A function to determine if the pressed key is an integer
function numberPressed(evt) {
  var charCode = (evt.which) ? evt.which : evt.keyCode;
  if (charCode > 31 && (charCode < 48 || charCode > 57) && (charCode < 36 || charCode > 40)) {
    return false;
  }
  return true;
}

// A function to format text to look like a phone number
function phoneFormat(input) {
  // Strip all characters from the input except digits
  input = input.replace(/\D/g, '');

  // Trim the remaining input to ten characters, to preserve phone number format
  input = input.substring(0, 10);

  // Based upon the length of the string, we add formatting as necessary
  var size = input.length;
  if (size == 0) {
    input = input;
  } else if (size < 4) {
    input = '(' + input;
  } else if (size < 7) {
    input = '(' + input.substring(0, 3) + ') ' + input.substring(3, 6);
  } else {
    input = '(' + input.substring(0, 3) + ') ' + input.substring(3, 6) + ' - ' + input.substring(6, 10);
  }
  return input;
}

Enter a phone number here: <input type="text" id="phoneNumber" onkeypress="return numberPressed(event);" />

关于javascript - 使用纯 JavaScript 将电话号码格式化为用户类型，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/30058927/