Get Loop Counter/Index Using For…Of Syntax in JavaScript

Get loop counter/index using for…of syntax in JavaScript

for…in iterates over property names, not values, and does so in an unspecified order (yes, even after ES6). You shouldn’t use it to iterate over arrays. For them, there’s ES5’s forEach method that passes both the value and the index to the function you give it:

var myArray = [123, 15, 187, 32];

myArray.forEach(function (value, i) {
    console.log('%d: %s', i, value);
});

// Outputs:
// 0: 123
// 1: 15
// 2: 187
// 3: 32

Or ES6’s Array.prototype.entries, which now has support across current browser versions:

for (const [i, value] of myArray.entries()) {
    console.log('%d: %s', i, value);
}

For iterables in general (where you would use a for…of loop rather than a for…in), there’s nothing built-in, however:

function* enumerate(iterable) {
    let i = 0;

    for (const x of iterable) {
        yield [i, x];
        i++;
    }
}

for (const [i, obj] of enumerate(myArray)) {
    console.log(i, obj);
}

demo

If you actually did mean for…in – enumerating properties – you would need an additional counter. Object.keys(obj).forEach could work, but it only includes own properties; for…in includes enumerable properties anywhere on the prototype chain.

Get loop counter/index using for…of syntax in JavaScript

for…in iterates over property names, not values, and does so in an unspecified order (yes, even after ES6). You shouldn’t use it to iterate over arrays. For them, there’s ES5’s forEach method that passes both the value and the index to the function you give it:

var myArray = [123, 15, 187, 32];

myArray.forEach(function (value, i) {
    console.log('%d: %s', i, value);
});

// Outputs:
// 0: 123
// 1: 15
// 2: 187
// 3: 32

Or ES6’s Array.prototype.entries, which now has support across current browser versions:

for (const [i, value] of myArray.entries()) {
    console.log('%d: %s', i, value);
}

For iterables in general (where you would use a for…of loop rather than a for…in), there’s nothing built-in, however:

function* enumerate(iterable) {
    let i = 0;

    for (const x of iterable) {
        yield [i, x];
        i++;
    }
}

for (const [i, obj] of enumerate(myArray)) {
    console.log(i, obj);
}

demo

If you actually did mean for…in – enumerating properties – you would need an additional counter. Object.keys(obj).forEach could work, but it only includes own properties; for…in includes enumerable properties anywhere on the prototype chain.

What is the simple way to get value and index on For of loop out of an array in Javascript / ReactNative?

use this

for (const [index, value] of array.entries()) {
  console.log(index, value);
}

Access to ES6 array element index inside for-of loop

Use Array.prototype.keys:

for (const index of [1, 2, 3, 4, 5].keys()) {  console.log(index);}

Using JavaScript count the number of elements equal to or higher than the index in a loop

You could reverse the array or sort descending, and find the index where the index (plus one) is greater than the value.

const
    values = [0, 0, 0, 1, 1, 2, 3, 3, 5, 6, 6, 7, 20, 20, 20],
    hIndex = [...values].reverse().findIndex((v, i) => v < i + 1);

console.log(hIndex);

How to get values from a object

Since dynamicList is an array - for in is not recommended ( you can check more here Why is using "for...in" for array iteration a bad idea? )

There are multiple array methods that you can use; in your case filter method is better:

 function deleteTask(id) {
 
        const shallowArray = dynamicList.filter( obj => obj.id !== id);

        displayTasks() 
      }

Also it is usually better not to mutate the data directly, but to create a copy

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