Why can\'t JavaScript strings have properties and how can you work around this limitation?

Why Can't JavaScript Strings Have Properties?

In JavaScript, there are eight primitive types: Undefined, Null, Boolean, Number, BigInt, String, Symbol, and the non-primitive type Object. Primitive values, such as strings, cannot have properties. Objects, on the other hand, can.

Attempting to add a property to a primitive value, such as a string, will result in a no-op in loose mode or a TypeError in strict mode. This is because JavaScript interprets such assignments as an attempt to set the variable's value, not create a new property.

<code class="js">var test = "test";
test.test = "test inner";
console.log(test); // "test"
console.log(test.test); // undefined</code>

Workarounds for Sorting Dates

While you can't add properties to strings, there are workarounds to facilitate date sorting in your grid:

ES5 Accessor Properties

ES5 introduced accessor properties, which allow you to define getter and setter functions for properties. You could define an accessor property on the String prototype that returns a date object:

<code class="js">Object.defineProperty(String.prototype, 'date', {
    get: function () {
      return new Date(this);
    }
});

var dateString = "2023-05-18";
var dateObject = dateString.date;
console.log(dateObject); // Date { 2023, 4, 18 ... }</code>

However, modifying the built-in String prototype is considered poor practice.

Define a Sorting Function

Alternatively, you could define a custom sorting function that recognizes date strings and compares them accordingly:

<code class="js">function compareDates(a, b) {
  var dateA = new Date(a);
  var dateB = new Date(b);

  return dateA - dateB;
}

var gridData = ["2023-05-18", "2022-12-15", "2021-08-23"];
gridData.sort(compareDates);
console.log(gridData); // ["2021-08-23", "2022-12-15", "2023-05-18"]</code>

Create a Custom Date Formatter

You could extend the JavaScript Date constructor with a custom formatting function that returns a sorted-friendly string representation:

<code class="js">Date.prototype.toSortedString = function () {
  return this.getFullYear() + "-" + (this.getMonth() + 1) + "-" + this.getDate();
};

var sortedByDate = dates.map(function (date) {
  return new Date(date).toSortedString();
});

sortedByDate.sort();
console.log(sortedByDate); // ["2021-08-23", "2022-12-15", "2023-05-18"]</code>

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