How to tell where an object value is undefined?-CodePudding

Below have I a very simple function, which I type check at compile and runtime, but I would to also rumtime check all the keys result in a value, and if it doesn't, then prompt where it broke.

The only solution I can think of is

assert(typeof db[customer] !== undefined);
assert(typeof db[customer].offers !== undefined);
assert(typeof db[customer].offers[offerId] !== undefined);
assert(typeof db[customer].offers[offerId][key] !== undefined);

but it is a lot of typing. I expected lodash would have a solution for this problem, but doesn't seem to be the case.

If I do

db?[customer]?.offers?[offerId]?[key] = value;

then I don't know where it returned undefined.

import assert from 'assert';

export function setPropertyOffer(
  db: Record<string, any>,
  customer: number,
  offerId: number,
  key: string,
  value: number | string,
) {
  assert(typeof db === 'object');
  assert(typeof customer === 'number');
  assert(typeof offerId === 'number');
  assert(typeof key === 'string');
  assert(typeof value === 'string' || typeof value === 'number');

  db[customer].offers[offerId][key] = value;
}

CodePudding user response：

You can use a function to help you decide. It takes an object, and an array (or arguments) of keys to get value.

var obj = [{
  "category1": {
    nested: {
      a: 'string',
      b: [69, 13, 15]
    }
  },
  "category2": "2",
}];

console.log(where_undefined(obj, 0, 'category1', 'nested', 'b', 2))
// print 15

console.log(where_undefined(obj, 0, 'category1', 'nested', 'b', 4))
// print undefined at key 4

function where_undefined(obj) {
  var args = Array.prototype.slice.call(arguments)
  args.shift();
  while (args.length) {
    var arg = args.shift();
    if (obj[arg] === undefined) {
      console.log("undefined at key "   arg);
      break;
    } else {
      obj = obj[arg];
    }
  }
  return obj;
}

CodePudding user response：

The simple answer is that you do don't or that it's irrelevant.

You get to pick the signature of your functions. If you need to reach deep down to your db argument, you are creating a dependency to the implementation details of that object.

Secondly, you get the decide what gets written to the database. If it's relevant that some property is never undefined, define it at the data schema level.