JavaScript Array Functions Cheat Sheet Part 3

 JavaScript Array Functions Cheat Sheet Part 3

indexOf()

indexOf() returns the first index at which element can be found.

Syntax

    arr.indexOf(searchElement[, fromIndex])

Example

    [ 1, 2, 3 ].indexOf(3) // 2

join()

join() returns string by concatenating all elements in array

Syntax

    arr.join([separator])

Example

     

    [ "x", "y", "z" ].join(" - ") 

    // "x - y - z"

keys() 

keys() returns Array Iterator that contains keys for each index

Syntax

    arr.keys()

Example

    ['a', 'b', 'c']

    .keys() // Array Iterator {  }

        .next() // { value: 0, done: false }

        .value // 0

lastIndexOf()

lastIndexOf() returns last index at which given element can be found.

Syntax

    

    arr.lastIndexOf(searchElement[, fromIndex])

    

Example

    1, 2, 3, 1, 0].lastIndexOf(1) // 3

    

map()

map() creates a new array with results of the provided function

Syntax

    let new_array = arr.map(

        function callback(currentValue[, index[, array]]) {

        // return element for new_array

    } [, thisArg])

Example

        [2, 3, 4].map(val => val * 2)

        // [ 4, 6, 8 ]

pop()

pop() removes last element from array and returns that element.

Syntax

        arr.pop()

Example

    const arr = [1, 2, 3]

    arr.push(1)

    // returns: 4 // arr is [ 1, 2, 3, 4 ]

reduce()

reduce() executes a reducer function, resulting in a single output value.

Syntax

        arr.reduce(

            callback(

                accumulator,

                currentValue[, index[, array]]

            )[, initialValue])

        

Example

        ['a', 'b', 'c'].reduce(

            (acc, curr) => acc + curr, 'd'

        ) // "dabc"

reduceRight()

reduceRight() executes a reducer function from right to left, resulting in single output value

Syntax

        arr.reduceRight(

            callback(accumulator,

                currentValue[, index[, array]])

            [, initialValue]

        )

Example

        [ 1, 2, 3 ].reverse() // [ 3, 2, 1 ]

Thanks for reading... 👏👏👏 

JavaScript Array Functions Cheat Sheet Part 2