Javascript – Dynamically generating Accessor and Mutation methods

This is a neat trick I picked up the other day, you can create a dynamic class which takes in a set of properties in the constructor and dynamically generates Accessor and/or Mutation methods (you just have to choose which lines to leave out):

function DynamicClass(properties) {
    // store class scope into a local variable
    var _this = this;

    for (var i in properties) {
        (function (i) {
            // create access method
            _this["get" + i] = function () {
                return properties[i];
            };

            // and mutation method, delete to make the class immutable
            _this["set" + i] = function (value) {
                properties[i] = value;
            }
        })(i);
    }
}

In your calling code, you can then create a new class like this, just define and provide the value for the properties you want to add to the class in the constructor call:

var obj = new DynamicClass({
    Name: "Dusty",
    Breed: "Highland Terrier",
    Age: 2
});

If you had added the mutation as well as the accessor methods, you’d be able to use them once the object has been created:

obj.setAge(3);
alert("Name: " + obj.getName() + ", Age: " + obj.getAge() + ", Breed:" + obj.getBreed());

Better still, if you’re using Visual Studio by any chance, intellisense will be able to pick up the dynamically generated get/set methods on your new dynamic class:

image

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Yan Cui

I’m an AWS Serverless Hero and the author of Production-Ready Serverless. I have run production workload at scale in AWS for nearly 10 years and I have been an architect or principal engineer with a variety of industries ranging from banking, e-commerce, sports streaming to mobile gaming. I currently work as an independent consultant focused on AWS and serverless.

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