JSFiddle - React, Tailwind, and code Playground

JavaScript

var names = ['John', 'Joe', 'Ralph'],
    data = [
        {
            id: 1,
            name: 'John'
        },
        {
            id: 2,
            name: 'Joseph'
        },
        {
            id: 3,
            name: 'ralph'
        }
    ],
    results = [];

var lnames = names.map(function(name) {
    return name.toLowerCase();
});

data.forEach(function(item) {
    if (lnames.indexOf(item.name.toLowerCase()) > -1) {
        results.push(item.id);
    }
});

console.log('found: ', results);