Question

149

How to update/add element of the array in JavaScript?

rated 0 times [ 153] [ 4] / answers: 1 / hits: 29903 / 10 Years ago, sun, november 2, 2014, 12:00:00

How can I update/add element in the array?

var persons = {

    data: []

};



var bob = {name: 'Bob', age: 15};

var fill = {name: 'Fill', age: 20};

var mark = {name: 'Mark', age: 19};

var john = {name: 'John', age: 4};



persons['data'].push(bob);

persons['data'].push(fill);

persons['data'].push(mark);

persons['data'].push(john);



var updatedJohn = {name: 'John', age: 100};



if (!persons['data'][updatedJohn.name]){

    persons['data'].push(updatedJohn);

} else {

    persons['data'][updatedJohn.name] = updatedJohn; // this line doesn't work

}

I can't figure out how to update an element of the array if element John already exist.

UPDATE

jsFiddle example

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

rickjordond

Add To Favorites

Follow

Total Points: 100

Total Questions: 105

Total Answers: 90

Location: Sweden

Member since Mon, May 8, 2023

1 Year ago

rickjordond questions

1 ReactJs get id instead of value from Material UI Autocomplete

Tue, Nov 30, 21, 00:00, 3 Years ago

1 Remix: middleware pattern to run code before loader on every request?

Mon, Nov 29, 21, 00:00, 3 Years ago

1 Why there is no physical client/build folder when i run nodejs server with react app as frontend

Wed, Jan 6, 21, 00:00, 3 Years ago

1 Await doesn't wait

Thu, May 2, 19, 00:00, 5 Years ago

1 dynamodb putItem callback function not working

Tue, Jan 15, 19, 00:00, 5 Years ago

View All

answered 10 Years ago tye · Accepted Answer

You will need a query function like the following to help you find indices according to a property in your database: (JSFiddle)

function findIndexByProperty(data, key, value) {

    for (var i = 0; i < data.length; i++) {

        if (data[i][key] == value) {

            return i;

        }

    }

    return -1;

}



var johnIndex = findIndexByProperty(persons.data, 'name', 'John');

if (johnIndex > -1) {

    persons.data[johnIndex] = updatedJohn;

} else {

    persons.data.push(updatedJohn);

}

Note that this only returns the first record with name John. You will need to decide what you want it to do in the case of multiple such records - update all of them? This kind of problem is why databases usually have unique keys to identify records.

If using Underscore or lodash you already have a _.findIndex() function that can be used instead:

var johnIndex = _.findIndex(persons.data, { name: 'John' });

2021 update: Using modern JavaScript you can replace the function with

const johnIndex = persons.data.findIndex(p => p.name === "John")