Indexof method in an object array?

javascript

prompt-engineering

functions

callbacks

byAnton Shumikhin·Dec 25, 2024

Quickly locate an object in an array by property using findIndex:

const items = [{id: 1, name: 'Alice'}, {id: 2, name: 'Bob'}];
//Because Bob is always elusive, isn't he?
const idx = items.findIndex(obj => obj.name === 'Bob');
console.log(idx);  // Outputs: 1, surprise! Bob was found.

Digging deeper: map and findIndex in Action

When you're looking for a specific property, combining findIndex with map is a nifty trick. Get the 'hello' property from every object and search for your value within the new array.

const data = [{hello: 'world'}, {hello: 'foo'}, {hello: 'bar'}];
const target = 'foo'; // Because everyone is always searching for 'foo'
const targetIndex = data.map(obj => obj.hello).indexOf(target);
console.log(targetIndex); // Outputs: 1, 'foo' was found, but where is 'bar'?

This oddly satisfying one-liner makes your code remarkably efficient.

Powering through with reduce

You can also channel the power of reduce to find the index without even breaking a sweat by doing manual iteration.

const target = 'foo'; // Yes, we are still looking for 'foo'
const targetIndex = data.reduce((acc, obj, index) => {
    // If 'foo' is found, take a break and return the index.
    return obj.hello === target ? index : acc;
}, -1);
console.log(targetIndex); // Outputs: 1, hey look, we found 'foo' again!

The -1 here is like your own personal Sherlock telling you that it found no match. It's the Watson of JavaScript!

Crafting your own solution: custom functions and libraries

Building your own search functions

For more specific searches, go ahead and create your arrayObjectIndexOf:

function arrayObjectIndexOf(array, searchFunction) {
    for (let i = 0; i < array.length; i++) {
        // If we find a match, abort the mission!
        if (searchFunction(array[i])) return i;
    }
    return -1; // We couldn't find it, time to pack up.
}

This customizable function can match objects based on multiple properties or complex conditions.

Harnessing the power of libraries

Libraries like Underscore.js offer methods _.pluck and _.findIndex to extract properties and find indexes:

const idx = _.findIndex(data, { hello: 'foo' });
console.log(idx); // Outputs: 1, Now Underscore.js found 'foo'!

These methods not only offer practicality but also cross-browser compatibility for those bearing legacy-related burdens

Handling edge cases and performance pains

Remember to handle edge cases when using findIndex or indexOf.

If the target doesn't exist, they return -1, emitting No-Signal.
The performance may vary depending on the size of the array or complexity of the condition.

If you are dealing with a larger-size array or with complex conditions, break or early return can be your saviours:

const idx = (() => {
    for (let [index, obj] of items.entries()) {
        // If 'Bob' is found lurking, unmask him and return index.
        if (obj.name === 'Bob') return index;
    }
    return -1;
})();
console.log(idx); // Outputs: 1, Caught ya, Bob!