Type Safety In JavaScript

type-safe-variables.js

class Variable {
  type;
  value;
  freeze;

  constructor(value, type, freeze = false) {
    if (!type) {
      this.type = typeof value;
    } else {
      this.type = type;
    }
    this.set(value);
    this.freeze = freeze;
  }

  get() {
    return this.value;
  }

  set(value) {
    if (this.freeze) {
      throw new Error("Cannot set value of a frozen variable");
    }

    if (this.type === "any") {
      this.value = value;
      return;
    }

    if (Array.isArray(this.type)) {
      if (!this.type.includes(typeof value)) {
        throwError(this.type, value);
      }
    } else {
      if (typeof value !== this.type) {
        throwError(this.type, value);
      }
    }

    this.value = value;

    function throwError(type, value) {
      throw new Error(
        `Cannot set value of variable to ${typeof value} of type ${
          Array.isArray(type) ? type.join(", ") : type
        }`
      );
    }
  }
}