javascript - JSON How to return an objects name instead of its value -

json objects have "name : value" relationship. need way return objects name instead of value.

for example, if animals[0].species return value "feline", how instead return name "species"?

the function i'm writing requires me check if objects name equal input of function before return value of object.

i have searched stackoverflow , w3schools solution, no success.

var animals = [ {     "animal": "cat",     "species": "feline",     "likes": "yarn",     "dislikes" : "water" }, {     "animal": "dog",     "species": "canine",     "likes": "rubber balls",     "dislikes": "thunder" } ];   function lookup(property){   if (animals[0].property == "species") {     return animals[0].species;   } } lookup("species"); 

you're missing quotes around species

function lookup(property) {   if (animals[0].property === 'species') { // see quotes ?     return animals[0].species;   } } 

that function using animals free variable , not useful if ever plan on using lookup on other object. writing function differently, can make more versatile

function lookup(object, property) {   if (object.hasownproperty(property)) {     return object[property];   }   return null; } 

now specific animal

lookup(animals[0], 'species'); // => 'feline' lookup(animals[1], 'species'); // => 'canine' lookup(animals[2], 'species'); // => null 

you can take 1 step further defining higher-order procedure

function getspecies(animal) {   return lookup(animal, 'species'); }  getspecies(animal[0]); // => 'feline' getspecies(animal[1]); // => 'canine' getspecies(animal[2]); // => null 

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per alex's comment, last part, use partial function application or curry lookup function.

const lookup = x => y => y.hasownproperty(x) ? y[x] : null; const species = lookup('species'); species(animal[0]); // => 'feline' species(animal[1]); // => 'canine' species(animal[2]); // => null