How to destructure nested objects in for-loop

You can use this:

for (let {user, age = "DEFAULT AGE", geo: {lat, long}} of users) {
  console.log(user, age, lat, long);

You have already successfully destructured user (simply by the property name in the object) and age (with a default value as well).

To use nested destructuring, step by step, simply put the property name geo in there as well, since that’s the next property on the objects you’re iterating over that contains your needed values:

{user, age = "DEFAULT AGE", geo} — this would yield {lat: "12", long: "13"} for geo.

To access the nested properties directly, follow the object structure:

{user, age = "DEFAULT AGE", geo: {}} — this would just validate that geo is indeed an object.

Then, list the properties you want to access in that object:

{user, age = "DEFAULT AGE", geo: {lat, long}} — this would yield "12" for lat and "13" for long.

You could even go a step further and rename those properties:

{user, age = "DEFAULT AGE", geo: {lat: latitude, long: longitude}} — this would yield "12" for latitude and "13" for longitude.

These are the basic cases for destructuring objects:

  • name means “just assign the entire value to name”.
  • {} means “check that the value to be destructured is an object or can be converted into one, i.e. is neither null nor undefined; create no variables”.
  • { prop } means “get the value of prop as the variable prop”.
  • { prop: rename } means “follow the prop property and get its value as the variable rename1.
  • { prop = value } means “get the value of prop as the variable prop, but assign value if prop yields undefined2.

For the “rename” case, the rules apply recursively: rename is like name, so it can be replaced by {}, or { anotherProp }, or { anotherProp: anotherRename }, or { anotherProp = anotherDefault }, etc.

Other properties on the same object level may be added via commas, like {propA, propB}.

For arrays, similar cases exist: [] would validate that the value to be destructured is an iterable object; [a, b] has the same meaning as {0: a, 1: b}; etc.

1: Note that in the case of { prop: something } no variable prop is created.

2: “yields undefined” means that obj.prop would be equal to undefined which means either that the property exists and has the literal value undefined or that the property doesn’t exist.

If you're just trying to find a given user and return the geo for it, this will do:

users.find( u => u.user === 'Name1' ).geo;

Keep in mind, you would want to do some checks aginst your 'find result' before trying to use it. For example:

const user = users.find( u => u.user === 'Name1' );

if (user && user.hasOwnProperty('geo')) {