KnockoutJS扩展程序不会再次使用相同的值进行格式化

ko.extenders.formatValue = function (target, format) {
  var formattedValue = ko.observable();
  var cachedValues = {};

  function formatValue(value) {
    // Check if the value is already formatted
    if (cachedValues[value] !== undefined) {
      return cachedValues[value];
    }

    // Format the value
    var formatted = // Your formatting logic here

    // Cache the formatted value
    cachedValues[value] = formatted;

    return formatted;
  }

  // Computed observable to format the value
  var result = ko.computed({
    read: function () {
      var value = target();
      return formatValue(value);
    },
    write: target
  });

  // Add a dispose callback to clear the cache when the observable is disposed
  result.dispose = function () {
    cachedValues = {};
    formattedValue.dispose();
  };

  return result;
};

var viewModel = {
  value: ko.observable().extend({ formatValue: "currency" })
};

// 在绑定时可以直接使用 value() 函数获取格式化后的值