Finding the index of an array element with multiple sub-elements in JavaScript

Question

Finding the index of an array element with multiple sub-elements in JavaScript

Currently, I am focusing on JavaScript and I have the task of finding the index of an element in an array.

const tasks = [{taskno:'1', todo:'cooking'},{taskno:'2', todo:'play'}];

My goal is to locate the index of the task with 'cooking' as its todo value, without knowing its task number. Is there a built-in function for this purpose?

I attempted to use the following code but it did not yield the desired result:

const index = tasks.indexOf({todo: 'cooking'});

Currently, I am resorting to using a for loop for this task. Are there any alternative methods available?

Your assistance is greatly appreciated :)

javascript arrays indexing

Answer 1

Answer №1

Finding the index of an object in an array using the indexOf function requires having a reference to that object beforehand.

For example:

var obj1 = { value: 'obj1' },
    obj2 = { value: 'obj2' };

[obj2, obj1].indexOf(obj1); //1

If you do not already have a reference to the object, you will need to implement your own custom search algorithm.

var tasks = [{taskNo:'1', action:'cooking'}, {taskNo:'2',action:'play'}];

var resultIndex = findIndexOfFirstMatch(tasks, function (item) {
    return item.action === 'cooking';
});

console.log(resultIndex); //0

function findIndexOfFirstMatch(array, matcherFunction) {
    var index = 0, length = array.length;

    for (; index < length; index++) {
        if (matcherFunction(array[index])) return index;
    }

    return -1;
}

Answer 2

Finding the index of an object in an array using the indexOf function requires having a reference to that object beforehand.

For example:

var obj1 = { value: 'obj1' },
    obj2 = { value: 'obj2' };

[obj2, obj1].indexOf(obj1); //1

If you do not already have a reference to the object, you will need to implement your own custom search algorithm.

var tasks = [{taskNo:'1', action:'cooking'}, {taskNo:'2',action:'play'}];

var resultIndex = findIndexOfFirstMatch(tasks, function (item) {
    return item.action === 'cooking';
});

console.log(resultIndex); //0

function findIndexOfFirstMatch(array, matcherFunction) {
    var index = 0, length = array.length;

    for (; index < length; index++) {
        if (matcherFunction(array[index])) return index;
    }

    return -1;
}

Answer 3

Answer №2

In order to locate the specific object rather than just its index, you have the option of employing the underscore library along with its findWhere method:

var desired_task = _findWhere(task, {todo: "Cooking"});

If your requirement is to find the index, then you can utilize the task_wanted variable to conduct a search within the array using the indexOf() function.

Answer 4

In order to locate the specific object rather than just its index, you have the option of employing the underscore library along with its findWhere method:

var desired_task = _findWhere(task, {todo: "Cooking"});

If your requirement is to find the index, then you can utilize the task_wanted variable to conduct a search within the array using the indexOf() function.

Finding the index of an array element with multiple sub-elements in JavaScript

Answer №1

Answer №2

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