JavaScript Array Methods | javaScript Tutorial for Beginners

陣列方法/Array methods

   

• Array pop() Method
• Array push() Method
• Array toString() Method
• Array join() Method
• Array splice() Method
• Array sort() Method
• Array shift() Method
• Array unshift() Method
• Array reverse() Method
• Array concat() Method
• Array slice() Method
• Array filter() Method
• Array find() Method
• Array forEach() Method
• Array map() Method
• Array reduce() Method
• Array some() Method
• Array every() Method

Array pop() Method

The “pop()” method is used when you want to remove the last element of an array. The method returns the removed items value.

Ex

  var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
  lang.pop();   

Result of the above example is: Output

 // New array: Python,Vuejs,Nodejs

2. Array push() Method

The “push()” method is used to add a new element to the end of an array.

Ex:

   var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
    lang.push("angular");   

Result of the above example is: Output

 // New array: Python,Vuejs,Nodejs,javascript,angular

3. Array toString() Method

The “toString()” method is used to convert array to string.

Ex:-

    var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
    lang.toString();    

Result of the above example is:

Python,Vuejs,Nodejs,javascript

Javascript – Remove Duplicates from Array

4. Array join() Method

The join() used to join the elements of an array into a string. The “join()” method puts all the elements of the array into a string list. This method difference from “toString()” method.

Ex:

    var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
     lang.join("-");

     var x = document.getElementById("demo");
     x.innerHTML = lang.join("-");

Result of the above example is: // output

Python-Vuejs-Nodejs-javascript

5. Array splice() Method

The “splice()” method can add and remove items form an array.

syntax

array.splice(index, howMany, [element1][, …, elementN]);

• index − Index param specifies where a new item should be inserted.
• howMany − An integer indicating the number of old array elements to remove.
• If howMany set to 0, no items will be removed in array list.

Ex:

    var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
    lang.splice(2, 0, "Mongodb", "Rust"); 

Result of the above example is: // Output

new array: Python,Vuejs,Mongodb,Rust,Nodejs,javascript

6. Array sort() Method

This method either alphabetic or numeric sorts an array.

Ex:

    var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
    lang.sort();

Result of the above example is:

// Outuput

array: Nodejs,Python,Vuejs,javascript

7. Array shift() Method

This method removes the first element of an array. like the “pop()” method, removes an element from an array.

Ex:-

  var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
  lang.shift(); 

Result of the above example is: // Output

new array: Vuejs,Nodejs,javascript

8. Array unshift() Method

The unshift() method adds a new element to the beginning of an array.

Ex:

    var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
    lang.unshift("Rust");   

Result of the above example is: //Output

New array: Rust,Python,Vuejs,Nodejs,javascript

9. Array reverse() Method

The method is used for reverses the order of the elements in an array.

Ex:

    var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
    lang.reverse();    

Result of the above example is: // Outuput

array: javascript,Nodejs,Vuejs,Python

10. Array concat() Method

The “concat()” method joins two or more arrays and makes a new one.

Ex:

    var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
    var newlang = ["Angular", "Rust"];      
    var join = lang.concat(newlang);    

Result of the above example is: // Output

New array: Python,Vuejs,Nodejs,javascript,Angular,Rust

11. Array slice() Method

The method is used to selected elements in an array and makes a new one. It can take one or two arguments.

Ex:

    var lang = ["Python", "Vuejs", "Nodejs", "javascript"];
    var cars = lang.slice(1, 4);  

Result of the above example is: //Output

New Array : Vuejs,Nodejs,javascript

12. Array filter() Method

This filter method is used to filter the array, according our conditions.

Ex:

var number = [10, 5, 16, 4, 6, 7, 12, 18, 20];

function isCheck(value) {
  return value > 9;
}

var filter = number.filter(isCheck);
document.getElementById("demo").innerHTML = filter;

Result of the above example is: Output

 //new array: 10,16,12,18,20

In this example the function filter() creates a new array. Those elements that satisfy the condition checked by isCheck() function.

13. Array find() Method

This find method is used find the first element of an array.

Ex:

var number = [10, 5, 16, 4, 6, 7, 12, 18, 20];

function isCheck(value) {
  return value >= 9;
}

var find = number.find(isCheck);
document.getElementById("demo").innerHTML = find;

Result of the above example is: Output

// 10

14. Array forEach() Method

The JavaScript Array Method – forEach () imposes a specific function for each item in a particular array individually:

Ex:

var num = [10, 5, 16, 4, 6, 7, 12, 18, 20];
 num.forEach(function(item) {
    document.writeln(item);
 });

Result of the above example is: Output

 // return 
10 5 16 4 6 7 12 18 20

15. Array map() Method

The map () method in JavaScript creates an array by calling a specific function on each element in the original array.

Ex:

var num = [4, 9, 16, 25];
var x = num.map(Math.sqrt);
document.write(x);

Result of the above example is: Output

 // return   
 2,3,4,5 

16. Array reduce() Method

The javascript array reduce() method reduces the array to a single value.

Ex:

var numArr = [
        {  name: 'a', num: 50},
        {  name: 'b', num: 50},
        {  name: 'c', num: 75},
        {  name: 'd', num: 35},
        {  name: 'e', num: 25 },
        {  name: 'f', num: 40 },
    ];

    var sum = numArr.reduce(function (total, currentValue) {
        return total + currentValue.num;
    }, 0);

    document.write( "javascript- Sum of the array value is :- " + sum );

Result of the above example is: Output

 // return  
 javascript- Sum of the array value is :- 275

17. Array some() Method

The javascript array some() method checks whether at least one element of the array matches the given predicate. if none of the array elements match the predicate, then it will return false

Ex:

var nums = [10, 12, 12, 20, 25];

function checkNumber(num) {
  return num >= 25;
}

document.write(nums.some(checkNumber));

Result of the above example is: Output

 // return   
 True

18. Array every() Method

The javascript array every() method checks whether all elements of the array match the predicate:

Ex:

var nums = [10, 12, 12, 20, 25];

function checkNumber(num) {
  return num >= 3;
}

document.write(nums.every(checkNumber));

Result of the above example is:

 // return   
 true