This method creates a read only wrapper around a javascript object, so that you can pass large object without copying them and still avoiding that they are changed.

wrapInReadOnlyProxy.js

function wrapInReadOnlyProxy(orig, throwOnSet = false) {
	if (typeof orig !== "object") {
		return orig;
	}
	
	return new Proxy(orig, {
		get: function(target, property) {
		if (property in target) {
			return wrapInReadOnlyProxy(target[property]);
		}
		return undefined;
		},
		set: function() {
			if (throwOnSet) {
				throw new Error("Can't set values on a readonly proxy");
			}
		}
	});
}

Example on how to use the wrapper:

let original = {
    a: 42,
    b: "forty-two",
    c: {
        e: 51,
        f: "FIFTY-ONE",
        g: {
            i: 101
        },
        h: ["one", "two", "three"]
    },
    d: [10, 20, 30]
};

let readonly = wrapInReadonlyProxy(original);

readonly.a = 142;
readonly.c.e = 151;
readonly.c.g.i = 1001;
readonly.d[1] = 123;

console.log("After trying to modify 'readonly'");
console.log("original", JSON.stringify(original));
console.log("readonly", JSON.stringify(readonly));

console.log();

original.a = 142;
original.c.e = 151;
original.c.g.i = 1001;
original.d[1] = 123;

console.log("After trying to modify 'original'");
console.log("original", JSON.stringify(original));
console.log("readonly", JSON.stringify(readonly));