Mastering JavaScript Functional Programming - Second Edition

Chapter 10, Ensuring Purity – Immutability

10.1. Freezing by proxying: As requested, using a proxy allows you to intercept changes on an object. (See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy for more on this.) We use recursion to apply the proxy all the way down in case some attributes are objects themselves:

const proxySetAll = obj => {  Object.keys(obj).forEach(v => {    if (typeof obj[v] === "object") {      obj[v] = proxySetAll(obj[v]);    }  });  return new Proxy(obj, {    set(target, key, value) {      throw new Error("DON'T MODIFY ANYTHING IN ME");    },    deleteProperty(target, key) {      throw new Error("DON'T DELETE ANYTHING IN ME");    }  });};

The following is the output of the preceding code. You'd probably require ...