Is it possible for the `findIndex` method in EcmaScript6 to return multiple values at once

Question

Is it possible for the `findIndex` method in EcmaScript6 to return multiple values at once

When delving into ES6, I came across a situation where I needed to find the index of multiple items in an Array. However, I found that it only returned the index of the first item that matched my condition or callback function.

For example, let's say we have an Array with ages and we want the indexes of all ages greater than or equal to 18.

let ages = [12,15, 18, 17, 21];
console.log(`Over 18: ${ages.findIndex(item => item >= 18)}`);
// expected output: [2,4]
// actual output: 2

So I'm curious if the Array.prototype.findIndex() method only returns the index of the first item that matches, or -1 if no item satisfies the condition. Is there a way to achieve this using ES6?

Thank you

javascript arrays ecmascript-6

Answer 1

Answer №1

To implement this functionality, utilize the .map() method as shown below:

let ages = [12, 15, 18, 17, 21];
let indexes = ages.map((elm, idx) => elm >= 18 ? idx : '').filter(String);
console.log( indexes );

The syntax for utilizing the .map() method is as follows:

var new_array = arr.map(function callback(currentValue[, index[, array]]) {
    // Return element for new_array
}[, thisArg])

In this syntax, both currentValue and index can be harnessed according to our needs.

An example of a reusable function for this task is demonstrated below:

const ages = [12, 15, 18, 17, 21];
const getAllIndexes = (arr, val) => {
  return arr.map((elm, idx) => elm >= val ? idx : '').filter(String);
}

console.log(getAllIndexes(ages, 18));
console.log(getAllIndexes(ages, 17));

Answer 2

To implement this functionality, utilize the .map() method as shown below:

let ages = [12, 15, 18, 17, 21];
let indexes = ages.map((elm, idx) => elm >= 18 ? idx : '').filter(String);
console.log( indexes );

The syntax for utilizing the .map() method is as follows:

var new_array = arr.map(function callback(currentValue[, index[, array]]) {
    // Return element for new_array
}[, thisArg])

In this syntax, both currentValue and index can be harnessed according to our needs.

An example of a reusable function for this task is demonstrated below:

const ages = [12, 15, 18, 17, 21];
const getAllIndexes = (arr, val) => {
  return arr.map((elm, idx) => elm >= val ? idx : '').filter(String);
}

console.log(getAllIndexes(ages, 18));
console.log(getAllIndexes(ages, 17));

Answer 3

Answer №2

The findIndex() function is utilized to locate the index of the initial element in the array that meets the criteria set by the testing function. If no elements satisfy the condition, -1 is returned.

An alternative approach involves utilizing reduce. By employing concat, the index can be added to the accumulator when the number is equal to or greater than 18.

let ages = [12, 15, 18, 17, 21];

let result = ages.reduce((c, v, i) => v >=18 ? c.concat(i) : c, []);

console.log(result);

Answer 4

The findIndex() function is utilized to locate the index of the initial element in the array that meets the criteria set by the testing function. If no elements satisfy the condition, -1 is returned.

An alternative approach involves utilizing reduce. By employing concat, the index can be added to the accumulator when the number is equal to or greater than 18.

let ages = [12, 15, 18, 17, 21];

let result = ages.reduce((c, v, i) => v >=18 ? c.concat(i) : c, []);

console.log(result);

Answer 5

Answer №3

For a straightforward solution, utilize the Array.reduce() method to create an array containing the indexes of all ages that are greater than 18.

let ages = [12,15, 18, 17, 21];
var result = ages.reduce((a,curr,index)=>{
  if(curr >= 18)
    a.push(index);
  return a;
},[]);
console.log(result);

Answer 6

For a straightforward solution, utilize the Array.reduce() method to create an array containing the indexes of all ages that are greater than 18.

let ages = [12,15, 18, 17, 21];
var result = ages.reduce((a,curr,index)=>{
  if(curr >= 18)
    a.push(index);
  return a;
},[]);
console.log(result);

Is it possible for the `findIndex` method in EcmaScript6 to return multiple values at once

Answer №1

Answer №2

Answer №3

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