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JavaScript: Move an array element from one position to another

JavaScript Array: Exercise-38 with Solution

Write a JavaScript function to move an array element from one position to another.

Test Data:
console.log(move([10, 20, 30, 40, 50], 0, 2));
[20, 30, 10, 40, 50]
console.log(move([10, 20, 30, 40, 50], -1, -2));
[10, 20, 30, 50, 40]

Pictorial Presentation:

JavaScript: Move an array element from one position to another

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript function to move an array element from one position to another.</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function move(arr, old_index, new_index) {
    while (old_index < 0) {
        old_index += arr.length;
    }
    while (new_index < 0) {
        new_index += arr.length;
    }
    if (new_index >= arr.length) {
        var k = new_index - arr.length;
        while ((k--) + 1) {
            arr.push(undefined);
        }
    }
     arr.splice(new_index, 0, arr.splice(old_index, 1)[0]);  
   return arr;
}

console.log(move([10, 20, 30, 40, 50], 0, 2));

console.log(move([10, 20, 30, 40, 50], -1, -2));

Sample Output:

[20,30,10,40,50]
[10,20,30,50,40]

Flowchart:

Flowchart: JavaScript: Move an array element from one position to another

ES6 Version:

function move(arr, old_index, new_index) {
    while (old_index < 0) {
        old_index += arr.length;
    }
    while (new_index < 0) {
        new_index += arr.length;
    }
    if (new_index >= arr.length) {
        let k = new_index - arr.length;
        while ((k--) + 1) {
            arr.push(undefined);
        }
    }
     arr.splice(new_index, 0, arr.splice(old_index, 1)[0]);  
   return arr;
}

console.log(move([10, 20, 30, 40, 50], 0, 2));

console.log(move([10, 20, 30, 40, 50], -1, -2));

Live Demo :

See the Pen JavaScript - Move an array element from one position to another-array-ex- 38 by w3resource (@w3resource) on CodePen.


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JavaScript: Tips of the Day

function and arguments

const person = {
  name: 'Lydia Hallie',
  hobbies: ['coding'],
};

function addHobby(hobby, hobbies = person.hobbies) {
  hobbies.push(hobby);
  return hobbies;
}

addHobby('running', []);
addHobby('dancing');
addHobby('baking', person.hobbies);

console.log(person.hobbies);

The addHobby function receives two arguments, hobby and hobbies with the default value of the hobbies array on the person object.
First, we invoke the addHobby function, and pass "running" as the value for hobby and an empty array as the value for hobbies. Since we pass an empty array as the value for y, "running" gets added to this empty array.
Then, we invoke the addHobby function, and pass "dancing" as the value for hobby. We didn't pass a value for hobbies, so it gets the default value, the hobbies property on the person object. We push the hobby dancing to the person.hobbies array.
Last, we invoke the addHobby function, and pass "bdaking" as the value for hobby, and the person.hobbies array as the value for hobbies. We push the hobby baking to the person.hobbies array.
After pushing dancing and baking, the value of person.hobbies is ["coding", "dancing", "baking"]

Ref: https://bit.ly/2Hcpkm6