method find javascript deep array object RN react native

问题

Here is a part of my object

const category = {
    fr: {
        list: [
            {id: 1, label: 'coucou'},
            {id: 2, label: 'moi'},
            {id: 3, label: 'ici'},
            {id: 4, label: 'maintenant'},
            {id: 5, label: 'demain'},
]}}
const lang = fr;
const anyId = 3;

I don't know why when doing the following:

const result = category[lang].list.find(item => item.id === anyId) console.log(result)

Throws the following:

// undefined category[lang].list.find(item => item.id === anyId) is not a function, or just undefined

same result for .map or .filter

console.log(category) returns no error
console.log(category[lang]) returns no error
console.log(category[lang].list) returns no error

but anything else will return an error. It drives me crazy, any help will be highly appreciated.

回答1:

Use const lang = "fr" instead of const lang = fr, because fr is an undefined variable but "fr" is a string. So you'll get category["fr"] instead of category[fr].

const category = {
    fr: {
        list: [
            {id: 1, label: 'coucou'},
            {id: 2, label: 'moi'},
            {id: 3, label: 'ici'},
            {id: 4, label: 'maintenant'},
            {id: 5, label: 'demain'},
]}}
const lang = "fr";
const anyId = 3;

const result = category[lang].list.find(item => item.id === anyId)

console.log(result)

回答2:

You want category.fr not just fr, as the variable fr does not exist.

Now that lang contains your fr object, you can simply do a .find() on lang.list as below:

const category = {
    fr: {
        list: [
            {id: 1, label: 'coucou'},
            {id: 2, label: 'moi'},
            {id: 3, label: 'ici'},
            {id: 4, label: 'maintenant'},
            {id: 5, label: 'demain'},
]}}

// Fill param from a variable, or anything, as long as it's a string:
const param = 'fr';
// Use brackets here, as you want `category.fr` and not `category.param`:
const lang = category[param];
//Or you can simply use:
//const lang = category.fr; //If this is not a parameter, or user input

const anyId = 3;

console.log(lang);

console.log(lang.list.find(item => item.id === anyId));

回答3:

It works on mdn sandbox

const category = {
    fr: {
        list: [
            {id: 1, label: 'coucou'},
            {id: 2, label: 'ici'},
            {id: 3, label: 'demain'},
            {id: 4, label: 'matin'},
          ]
    }
};
var lang ='fr';
var catID = 3;
console.log(lang);
console.log(catID);
console.log(category);
console.log(category[lang]);
console.log(category[lang].list);
var found = category[lang].list.find(function(element) {
   return element.id === catID;
});

console.log(found.label); // demain

just add a return inside the callback function, but it still doesn't work on react-native so the problem remains

来源：https://stackoverflow.com/questions/48951612/method-find-javascript-deep-array-object-rn-react-native

标签

javascript

object

react-native

find