Query an array of objects and return the target-CodePudding

I need to find an object in an array by a key and value

I'm trying to do a search on an array of objects with for in. but I can not.

My input:

findObject[{ a: 1, b: { c: 2 } }, { a: 1, b: { c: 3 } }, { c: 3 }] //the last argument ({ c: 3 }) is the target

What I'm trying to return:

{ a: 1, b: { c: 3 } }

Note: The array of objects can have any object and the target too

CodePudding user response：

You can use Array.find to find the item in the array whose values contain an object whose c property is 3:

const arr = [{ a: 1, b: { c: 2 } }, { a: 1, b: { c: 3 } }, { c: 3 }]
const result = arr.find(e => Object.values(e).some(k => k.c == 3))
console.log(result)

CodePudding user response：

What the OP is looking for is a find using deep equality (keys and values, including nested keys and values are equal). Even shallow equality is a deep topic in JS and applying it recursively is even deeper.

A fast but flawed idea is comparing JSON encodings for the two objects being compared. I wave a hand at that in the snippet, but prefer to use a utility that has thought through edge cases and probably executes fast.

function isEqual(a, b) {
  // not good, but quick to code:
  // return JSON.stringify(a) === JSON.stringify(b)
  
  // lodash has put some thought into it
  return _.isEqual(a, b)
}

// find the first object in  array with a value deeply equal to object
function findObject(array, object) {
  return array.find(el => {
    return Object.values(el).some(v => isEqual(v, object))
  })
}


let array = [{ a: 1, b: { c: 2 } }, { a: 1, b: { c: 3, d: { e: "hi" }} }];
let object = { c: 3, d: { e: "hi" }};

let result = findObject(array, object);
console.log(result);

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js"></script>

The OP asks to find the last object of an array as the target in the array up to that point. Adopt as follows...

// array is the array to search plus the last item is the thing to search for
let firstObjects = array.slice(0, -1)
let lastObject = array.at(-1)
let result = findObject(firstObjects, lastObject)