How to find a value in an array of objects in JavaScript?

If you have an array such as

var people = [  { "name": "bob", "dinner": "pizza" },  { "name": "john", "dinner": "sushi" },  { "name": "larry", "dinner": "hummus" }];

You can use the filter method of an Array object:

people.filter(function (person) { return person.dinner == "sushi" });  // => [{ "name": "john", "dinner": "sushi" }]

In newer JavaScript implementations you can use a function expression:

people.filter(p => p.dinner == "sushi")  // => [{ "name": "john", "dinner": "sushi" }]

You can search for people who have "dinner": "sushi" using a map

people.map(function (person) {  if (person.dinner == "sushi") {    return person  } else {    return null  }}); // => [null, { "name": "john", "dinner": "sushi" }, null]

or a reduce

people.reduce(function (sushiPeople, person) {  if (person.dinner == "sushi") {    return sushiPeople.concat(person);  } else {    return sushiPeople  }}, []); // => [{ "name": "john", "dinner": "sushi" }]

I'm sure you are able to generalize this to arbitrary keys and values!

jQuery has a built-in method jQuery.grep that works similarly to the ES5 filter function from @adamse's Answer and should work fine on older browsers.

Using adamse's example:

var peoples = [  { "name": "bob", "dinner": "pizza" },  { "name": "john", "dinner": "sushi" },  { "name": "larry", "dinner": "hummus" }];

you can do the following

jQuery.grep(peoples, function (person) { return person.dinner == "sushi" });  // => [{ "name": "john", "dinner": "sushi" }]

var getKeyByDinner = function(obj, dinner) {    var returnKey = -1;    $.each(obj, function(key, info) {        if (info.dinner == dinner) {           returnKey = key;           return false;         };       });    return returnKey;       }

jsFiddle.

So long as -1 isn't ever a valid key.