Locating the index of an array within another array using JavaScript

Question

Locating the index of an array within another array using JavaScript

Seeking the index of an array within another array in JavaScript, demonstrated as follows:

const piece = [5, 10];
const array = [[5, 10], [5, 11]];

//Using indexOf
console.log(array.indexOf(piece));

//Using findIndex
console.log(array.findIndex(function(element) {
  return element == piece;
  }));

The expected outcome is for both methods to return a 0, signifying the index at which "piece" exists within the larger array. However, both methods are returning -1.

Any insights into why this discrepancy may be occurring? And suggestions for an alternative approach?

Appreciate it!

javascript arrays

Answer 1

Answer №1

To easily compare the actual values, consider utilizing the JSON.stringify() method:

numbers = [3, 7];
values = [[3, 7], [3, 8]];

// Using findIndex
console.log(values.findIndex(function(item) {
    return JSON.stringify(item) == JSON.stringify(numbers);
    }));

Answer 2

To easily compare the actual values, consider utilizing the JSON.stringify() method:

numbers = [3, 7];
values = [[3, 7], [3, 8]];

// Using findIndex
console.log(values.findIndex(function(item) {
    return JSON.stringify(item) == JSON.stringify(numbers);
    }));

Answer 3

Answer №2

When comparing objects (arrays) that were created individually, they are not considered the same objects. To determine if their contents are identical, you can compare each integer within the arrays and ensure that the array lengths match:

piece = [5, 10];
array = [[5, 10], [5, 11]];

//Using findIndex
console.log(array.findIndex(function(element) {
  return element.length === array.length 
      && element.every((val, i) => val == piece[i]);
}));

Answer 4

When comparing objects (arrays) that were created individually, they are not considered the same objects. To determine if their contents are identical, you can compare each integer within the arrays and ensure that the array lengths match:

piece = [5, 10];
array = [[5, 10], [5, 11]];

//Using findIndex
console.log(array.findIndex(function(element) {
  return element.length === array.length 
      && element.every((val, i) => val == piece[i]);
}));

Answer 5

Answer №3

When working with arrays in JavaScript, it's important to understand that they are compared by reference rather than value. For example, consider two arrays a and b:

const a = [1, 2];
const b = [1, 2];

Using the comparison operators == or === to compare these arrays will actually be comparing their references, not the actual values within them. Therefore, console.log(a == b) or console.log(a === b) will return false.

Answer 6

When working with arrays in JavaScript, it's important to understand that they are compared by reference rather than value. For example, consider two arrays a and b:

const a = [1, 2];
const b = [1, 2];

Using the comparison operators == or === to compare these arrays will actually be comparing their references, not the actual values within them. Therefore, console.log(a == b) or console.log(a === b) will return false.

Locating the index of an array within another array using JavaScript

Answer №1

Answer №2

Answer №3

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