push():Adds one or more elements to the end of the array and returns the new length.
let arr = [1, 2, 3]; arr.push(4); // Now the value of arr is [1, 2, 3, 4]
pop(): Removes the element at the end of the array and returns the value of the element.
let arr = [1, 2, 3]; let removedElement = arr.pop(); //The value of removedElement is 3, and the value of arr is [1, 2]
shift():Delete the first element of the array and return the value of the element.
let arr = [1, 2, 3]; let removedElement = arr.shift(); //The value of removedElement is 1, the value of arr is [2, 3]
unshift():Adds one or more elements to the beginning of the array and returns the new length.
let arr = [2, 3]; arr.unshift(1); // Now the value of arr is [1, 2, 3]
concat(): Used to merge two or more arrays and return a new array.
let arr1 = [1, 2]; let arr2 = [3, 4]; let newArr = arr1.concat(arr2); //The value of newArr is [1, 2, 3, 4]
slice():Returns selected elements from an existing array.
let arr = [1, 2, 3, 4, 5]; let newArr = arr.slice(1, 3); //The value of newArr is [2, 3]
splice(): Adds/removes items to/from the array and returns the removed item.
let arr = [1, 2, 3, 4, 5]; let removed = arr.splice(1, 2); //The value of removed is [2, 3], the value of arr is [1, 4, 5]
indexOf(): Returns the index of the first occurrence of the specified element in the array, or -1 if it does not exist.
let arr = [1, 2, 3, 4, 3, 5]; let index = arr.lastIndexOf(3); //The value of index is 4
lastIndexOf(): Returns the index of the last occurrence of the specified element in the array, or -1 if it does not exist.
let arr = [1, 2, 3, 4, 3, 5]; let index = arr.lastIndexOf(3); //The value of index is 4
forEach(): Execute the provided function once for each element of the array.
let arr = [1, 2, 3]; arr.forEach(function(element) { console.log(element); }); //Console output: // 1 // 2 // 3
map(): Creates a new array whose result is the result of calling a provided function on each element in the array.
let arr = [1, 2, 3]; let newArr = arr.map(function(element) { return element * 2; }); // The value of newArr is [2, 4, 6]
filter():Creates a new array containing all elements of the test implemented by the provided function.
let arr = [1, 2, 3, 4, 5]; let newArr = arr.filter(function(element) { return element > 2; }); //The value of newArr is [3, 4, 5]
reduce():Execute a function you provide on each element in the array and aggregate its results into a single return value.
let arr = [1, 2, 3, 4]; let sum = arr.reduce(function(accumulator, current) { return accumulator + current; }, 0); //The value of sum is 10
every(): Check whether all elements in the array meet the specified conditions.
let arr = [1, 2, 3, 4, 5]; let allGreaterThanZero = arr.every(function(element) { return element > 0; }); // The value of allGreaterThanZero is true
some(): Check whether some elements in the array meet the specified conditions.
let arr = [1, 2, 3, 4, 5]; let someGreaterThanFour = arr.some(function(element) { return element > 4; }); // the value of someGreaterThanFour is true
find(): Returns the value of the first element in the array that satisfies the provided test function. Otherwise, undefined is returned.
let arr = [1, 2, 3, 4, 5]; let firstGreaterThanTwo = arr.find(function(element) { return element > 2; }); // The value of firstGreaterThanTwo is 3
findIndex(): Returns the index of the first element in the array that satisfies the provided test function. Otherwise, -1 is returned.
let arr = [1, 2, 3, 4, 5]; let index = arr.findIndex(function(element) { return element > 2; }); //The value of index is 2
includes(): Determine whether the array contains a specific value, if so, return true, otherwise return false.
let arr = [1, 2, 3, 4, 5]; let hasThree = arr.includes(3); // The value of hasThree is true
reverse(): Reverse the order of elements in the array.
let arr = [1, 2, 3, 4, 5]; arr.reverse(); // Now the value of arr is [5, 4, 3, 2, 1]
sort(): Sorts the array elements and returns the sorted array.
let arr = [3, 1, 2, 5, 4]; arr.sort(); // Now the value of arr is [1, 2, 3, 4, 5]
join(): Join all elements in the array into a string.
let arr = ["Hello", "World", "!"]; let joinedString = arr.join(" "); //The value of joinedString is "Hello World!"
toString():Convert the array to a string and return the result.
let arr = [1, 2, 3]; let arrString = arr.toString(); // The value of arrString is "1,2,3"
isArray(): Determines whether a variable is an array type. If so, it returns true, otherwise it returns false.
let arr = [1, 2, 3]; let isArr = Array.isArray(arr); // The value of isArr is true
fill(): Fills all elements in the array from the starting index to the ending index with a fixed value.
let arr = [1, 2, 3, 4, 5]; arr.fill(0, 1, 3); // Now the value of arr is [1, 0, 0, 4, 5]
flat(): Concatenate all sub-array elements into a new array and return it, the depth can be specified.
let arr = [1, 2, [3, 4, [5, 6]]]; let newArr = arr.flat(2); //The value of newArr is [1, 2, 3, 4, 5, 6]
from(): Create a new array instance from an array-like object or iterable object.
let arr = Array.from('hello'); // The value of arr is ['h', 'e', 'l', 'l', 'o']
keys(): Returns an Array Iterator object containing each index key in the array.
let arr = ['a', 'b', 'c']; let iterator = arr.keys(); for (let key of iterator) { console.log(key); } //Console output: // 0 // 1 // 2
values(): Returns a new Array iterator object containing the values for each index of the array.
let arr = ['a', 'b', 'c']; let iterator = arr.values(); for (let value of iterator) { console.log(value); } //Console output: // 'a' // 'b' // 'c'
entries(): Returns a new Array iterator object containing the key/value pairs for each index in the array.
let arr = ['a', 'b', 'c']; let iterator = arr.entries(); for (let entry of iterator) { console.log(entry); } //Console output: // [0, 'a'] // [1, 'b'] // [2, 'c']