How to check in JavaScript if object is in array with multiple objects?

Question

I have an array given with multiple objects as entries (collection) and I want to check if another source object is in those single entry objects. If so I want to return an array with all the objects that fulfill that condition. Here is the code with an example:

function whatIsInAName(collection, source) {
 var arr = [];
 var sourceEntries = Object.entries(source);
 for (var i = 0; i < collection.length; i++) {
 for (var j = 0; i < sourceEntries.length; i ++) {
 if((collection[i].hasOwnProperty(sourceEntries[j][0]))) {
 if(collection[i][sourceEntries[j][0]] == sourceEntries[j][1]) {
 /*what happens here*/
 }
 }
 arr.push(collection[i]);
 }
 }
 return arr;
}
print(whatIsInAName([{ "a": 1, "b": 2 }, { "a": 1 }, { "a": 1, "b": 2, "c": 2 }], { "a": 1, "b": 2 }));

Obviously I don't know what to put where it's written ("what happens here"). The problem is basically that the second for loop and both if conditions have to be true so the push command makes sense.

I appreciate any hint or help , thanks!

P.S. I know that this is probably not the most elegant way to solve it so happy about any other solutions as well.

• Arnav Aggarwal: Can you give a sample input and output? I think that would help someone figure out exactly what you need.
• Jhecht: I mean depending how thorough you really want to be, you could just test if JSON.stringify(item_in_array) == JSON.stringify(search_object)
• Mickey Mahoney: Of course, @ArnavAggarwal ! So basically what it is in the print statement is the input, output should be: [{"a": 1, "b": 2}, {"a": 1, "b": 2, "c": 3}] because those two objects contain both 'a' and 'b'.

Answer 1

This is where the built-in .filter function comes in handy:

function whatIsInAName(collection, source) {
 return collection.filter((obj) => {
 for (var prop in source) {
 if (source[prop] !== obj[prop]) {
 // The source property is not found in obj - no good!
 return false;
 }
 // The source property matches one of the obj's properties - keep going!
 }
 // Made it through the checks! You've got a match!
 return true;
 });
}
console.log(whatIsInAName([{
 "a": 1,
 "b": 2
}, {
 "a": 1
}, {
 "a": 1,
 "b": 2,
 "c": 2
}], {
 "a": 1,
 "b": 2
}));

Or, if you're inclined to use a library to do this, it can be done very simply with Lodash:

var collection = [{ "a": 1, "b": 2 }, { "a": 1 }, { "a": 1, "b": 2, "c": 2 }],
 source = { "a": 1, "b": 2 };
console.log(_.filter(collection, source));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

• Mickey Mahoney: Thanks, @j-titus Smooth and elegant way to solve it. Very much appreciated!