JavaScript Array Methods You Should Know

Arrays are an essential part of JavaScript programming, providing a powerful way to store and manipulate collections of data. In this article, we will explore eighteen fundamental array methods that every JavaScript programmer should know to write more efficient and clear code.

1. Push

The arr.push(..element) method adds a new element to the end of an array and returns the new length of the array. This method changes the original array.

Syntax:

arr.push(element1, element2, …)

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Example:

let arr = [1, 2, 3];
arr.push(4); // arr agora é [1, 2, 3, 4]

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2. Pop

The arr.pop() method removes the last element from an array and returns the removed element. This method also changes the original array and its length.

Syntax:

arr.pop()

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Example:

let arr = [1, 2, 3, 4];
arr.pop(); // arr agora é [1, 2, 3]

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3. Shift

The arr.shift() method removes the first element from an array and returns the removed element. This method also changes the length of the original array.

Syntax:

arr.shift()

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Example:

let arr = [1, 2, 3, 4];
arr.shift(); // arr agora é [2, 3, 4]

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4. Unshift

The arr.unshift(elements) method adds one or more elements to the beginning of an array and returns the new length of the array.

Syntax:

arr.unshift(item1, item2, …)

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Example:

let arr = [2, 3, 4];
arr.unshift(1); // arr agora é [1, 2, 3, 4]

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5. Splice

The arr.splice() method modifies the original array by removing, replacing or adding elements.

Syntax:

array.splice(start[, deleteCount[, item1[, item2[, ...]]]])

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Example:

let arr = [1, 2, 3, 4];
arr.splice(1, 1); // arr agora é [1, 3, 4]

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6. Slice

The arr.slice() method selects a part of an array and returns a new array with the items copied from the beginning index to the end. The original array is not changed.

Syntax:

arr.slice(start, end)

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Example:

let arr = [1, 2, 3, 4];
let newArr = arr.slice(1, 3); // newArr é [2, 3]

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7. Includes

The arr.includes(item, index) method checks if the item is present in the array from the given index and returns true if found, otherwise returns false.

Syntax:

arr.includes(item, index)

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Example:

let arr = [1, 2, 3, 4];
arr.includes(3); // true

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8. forEach

The arr.forEach() method executes a given function once for each element of the array.

Syntax:

arr.forEach(callback)

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Example:

let arr = [1, 2, 3, 4];
arr.forEach(num => console.log(num)); // imprime 1, 2, 3, 4

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9. Join

The arr.join(separator) method creates a string with all the elements of an array concatenated, separated by a specific delimiter.

Syntax:

arr.join(separator)

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Example:

let arr = [1, 2, 3, 4];
arr.join('-'); // "1-2-3-4"

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10. toString

The arr.toString() method converts an array to a string and returns the result.

Syntax:

arr.toString()

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Example:

let arr = [1, 2, 3, 4];
arr.toString(); // "1,2,3,4"

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11. Map

The map() method calls a callback function on each element of the original array and returns a new array with the results. This is a non-mutating method.

Syntax:

  arr.map(function callback(currentValue, index, array) {
    // Retorna um novo valor
  })

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Example:

let arr = [1, 2, 3, 4];
let doubled = arr.map(num => num * 2); // [2, 4, 6, 8]

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12. Reduce

The reduce() method applies a function to an accumulator and each array element (from left to right) to reduce to a single value.

Syntax:

arr.reduce(function callback(accumulator, currentValue, index, array) {
  // Retorna o valor acumulado
}, initialValue)

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Example:

let arr = [1, 2, 3, 4];
let sum = arr.reduce((acc, num) => acc + num, 0); // 10

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13. Filter

The filter() method creates a new array with all the elements that passed the test implemented by the provided function.

Syntax:

arr.filter(function callback(element, index, array) {
  // Retorna true para manter o elemento
})

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Example:

let arr = [1, 2, 3, 4];
let even = arr.filter(num => num % 2 === 0); // [2, 4]

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14. Sort

The sort() method arranges the elements of an array in ascending order or according to the given comparison function.

Syntax:

arr.sort([compareFunction])

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Example:

let arr = [4, 2, 3, 1];
arr.sort(); // [1, 2, 3, 4]

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15.Find

The find() method returns the first element in the array that satisfies the given test function.

Syntax:

arr.find(function callback(element, index, array) {
  // Retorna true para encontrar o elemento
})

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Example:

let arr = [1, 2, 3, 4];
let found = arr.find(num => num > 2); // 3

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16. IndexOf

The indexOf() method returns the first index at which a given element can be found in the array, or -1 if the element is not present.

Syntax:

arr.indexOf(searchElement, fromIndex)

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Example:

let arr = [1, 2, 3, 4];
let index = arr.indexOf(3); // 2

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17. Add

The some() method tests whether at least one element in the array passes the implemented test function.

Syntax:

arr.some(function callback(element, index, array) {
  // Retorna true se pelo menos um elemento passar no teste
})

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Example:

let arr = [1, 2, 3, 4];
let hasEven = arr.some(num => num % 2 === 0); // true

18. Concat

O método concat() é usado para mesclar dois ou mais arrays.

Sintaxe:

arr.concat(array2, array3, ..., arrayN)

Exemplo:

let arr1 = [1, 2];
let arr2 = [3, 4];
let merged = arr1.concat(arr2); // [1, 2, 3, 4]

Esses métodos são fundamentais para trabalhar com arrays em JavaScript. Dominar esses métodos permitirá que você manipule dados de forma mais eficiente e escreva códigos mais limpos e legíveis. Feliz codificação!

Referências:

• 10 Important JavaScript Array Methods You Must Know
• Lists of Top 10 JavaScript array methods a beginner Js developer should know

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