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30-seconds-of-code/snippets/js/s/function-based-object-property-matches.md
Angelos Chalaris 9d032ce05e Rename js snippets
2023-05-19 20:23:47 +03:00

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---
title: Matches object properties based on function
type: snippet
language: javascript
tags: [object]
cover: watermelon-bike
dateModified: 2020-10-21T21:54:53+03:00
---
Compares two objects to determine if the first one contains equivalent property values to the second one, based on a provided function.
- Use `Object.keys()` to get all the keys of the second object.
- Use `Array.prototype.every()`, `Object.prototype.hasOwnProperty()` and the provided function to determine if all keys exist in the first object and have equivalent values.
- If no function is provided, the values will be compared using the equality operator.
```js
const matchesWith = (obj, source, fn) =>
Object.keys(source).every(key =>
obj.hasOwnProperty(key) && fn
? fn(obj[key], source[key], key, obj, source)
: obj[key] == source[key]
);
```
```js
const isGreeting = val => /^h(?:i|ello)$/.test(val);
matchesWith(
{ greeting: 'hello' },
{ greeting: 'hi' },
(oV, sV) => isGreeting(oV) && isGreeting(sV)
); // true
```