JS-ES6 Cheatsheet Arrays

arrays.js

//Arrays elements could be with different types
let user = ["Ariel", 24, "Diaz"];
let [name, age, lastname] = user;


var arr = ["Pear", "Apple", "Orange"];

//CHECK IF IS AN ARRAY
console.log(Array.isArray(arr));

//CREATE FROM
//Static method creates a new, shallow-copied Array instance from an array-like or iterable object
console.log(Array.from(arr[0]));

// PUSH
//Adds one or more elements to the end of an array and returns the new length of the array
console.log("Array new length : ", arr.push("Mango"));

// POP
//Removes the last element from an array and returns that element
console.log("Deleted : ", arr.pop());

// UNSHIFT 
//Adds one or more elements to the beginning of an array and returns the new length of the array
console.log("Array new length : ", arr.unshift("Strawberry", "Cherry"));

// SHIFT
//Removes the first element from an array and returns that removed element
console.log("Deleted : ", arr.shift());


//REMOVE DUPLICATE VALUES USING SET
//Returns a new array
console.log([...new Set(arr)]);
console.log(Array.from(new Set(arr))); //Same operation

//SPLICE
//Changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.
console.log(arr);
arr.splice(1, 0, "Peach"); //Add peach at position 1
console.log(arr);
arr.splice(4, 1); //Remove one element at position 4
console.log(arr);
arr.splice(4, 1, "Watermelon"); //Replace element at position 4
console.log(arr);

// SLICE 
//Returns a shallow copy of a portion of an array into a new array object selected from start to end 
console.log(arr.slice(3)); //Starting in  position 3
console.log(arr.slice(1, 3)); //Values between position 1 and 3.
console.log(arr.slice(-2)); //Last 2 values.


//FIND
//Returns the first element in the provided array that satisfies the provided testing function
console.log(arr.find(a => a === "Apple") ? "Yes Apple" : "No Apple");

// INCLUDES
//Return a boolean if whether an array includes a certain value among its entries
console.log(arr.includes("Apple") ? "Found" : "Not found");


//FIND INDEX
//Returns the index of the first element in the array that satisfies the provided testing function
let appleIndex = arr.findIndex(a => a === "Apple");
console.log(appleIndex !== -1 ? `Apple is at ${appleIndex}` : "No Apple");


//INDEX OF
//Returns the first index at which a given element can be found in the array
let orangeIndex = arr.indexOf("Orange", 2); //Starting at 2 position
console.log(orangeIndex !== -1 ? `Orange is at ${orangeIndex}` : "No Orange");


//LAST INDEX OF
//Returns the last index at which a given element can be found in the array
arr.push('Orange');
let orangeLastIndex = arr.lastIndexOf("Orange");
console.log(orangeLastIndex !== -1 ? `Orange is at ${orangeLastIndex}` : "No Orange");

//SOME
//Tests whether at least one element in the array passes the test implemented by the provided function
console.log(arr.some(a => a === 'Orange'));

//TO STRING
//Returns a string representing the specified array and its elements
console.log(arr.toString());

//TO LOCALESTRING
//Returns a string representing the elements of the array. The elements are converted to Strings using their toLocaleString
console.log(arr.toLocaleString());

//JOIN
//Returns a new string by concatenating all of the elements in an array (or an array-like object), separated by commas or a specified separator string
console.log(arr.join(" - "));

//CONCAT
//Returns a new array  merge two or more arrays
let newArr = arr.concat(["Blackberry", "Kiwi"], ['Pineapple']);
console.log(newArr);

//FLAT
//Creates a new array with all sub-array elements concatenated into it recursively up to the specified depth
arr.push(["Blackberry", "Kiwi"]);
console.log(arr.flat());
arr = arr.flat();

//flat any deep
const ARRAY_DEEP = Infinity;
arr.flat(ARRAY_DEEP);

//FILTER
//Creates a new array with all elements that pass the test implemented by the provided function
console.log(arr.filter(a => a.length < 6));


//EVERY
//Tests whether all elements in the array pass the test implemented by the provided function. It returns a Boolean value
console.log(arr.every(a => a.length > 3));

//SORT
//Sorts the elements of an array in place and returns the sorted array, by default sort order is ascending.
console.log(arr.sort());
console.log(arr.sort((a, b) => a > b ? -1 : 1));

//REVERSE
//The first array element becomes the last, and the last array element becomes the first.
console.log(arr.reverse());


//FOR EACH
//Executes a provided function once for each array element
arr.forEach(e => console.log(e));

//MAP 
//Creates a new array populated with the results of calling a provided function on every element in the calling array.
let obj = arr.map(e => {
    return {
        name: e,
        quantity: Math.floor(Math.random() * (10))
    }
});
console.log(obj);

//REDUCE 
//executes a user-supplied "reducer" callback function on each element of the array, in order, passing in the return value from the calculation on the preceding element
const total = obj.reduce((accumulator, currentValue) =>
    accumulator + currentValue.quantity, 0 //Accumulator started in 0
);
console.log(total);

//REDUCE RIGTH 
//Applies a function against an accumulator and each value of the array (from right-to-left) to reduce it to a single value.
const word = obj.reduceRight((accumulator, currentValue) =>
    accumulator + currentValue.name[0], '' //Accumulator started in 0
);
console.log(word);

//TODO
//flatMap()
//fill()