JSFiddle - React, Tailwind, and code Playground

JavaScript

// для примера
items = [
	{market_hash_name: "item_1"}, 
	{market_hash_name: "item_2"}, 
	{market_hash_name: "item_3"}, 
	{market_hash_name: "item_3"}, 
	{market_hash_name: "item_2"},  
	{market_hash_name: "item_4"}, 
	{market_hash_name: "item_3"}, 
	{market_hash_name: "item_4"}
];
// для примера
g_ItemName = ["item_4", "item_1", "item_3", "item_3", "item_1", "item_4", "item_5"];

// g_ItemName - массив с вещами которые будем искать в инвентаре
for(var j = 0; j < g_ItemName.length; j++){
	var sendItemName = g_ItemName[j];
	if(g_ItemName.indexOf(sendItemName) !== j){
		continue;
	}
	if (search(sendItemName, items)) {
		console.log('Вещь: ' + sendItemName + ' найдена в инвентаре');
	}
	else{	
		console.log('Вещь: ' + sendItemName + ' не найдена в инвентаре');
	}
}

function search(name, items) {
	var otvet = false;
	for(var i = 0; i < items.length; i++){
		if (name == items[i].market_hash_name) {
			return true;
		}
		else{	
			otvet = false;
		}
	}
	return otvet;
}