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JavaScript: Create a new string taking the first and last n characters from a given string

JavaScript Basic: Exercise-68 with Solution

Write a JavaScript program to create a new string taking the first and last n characters from a given string. The string length must be greater or equal to n.

Pictorial Presentation:

JavaScript: Create a new string taking the first and last n characters from a given string

Sample Solution:

HTML Code:

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JavaScript program to create a new string using the first and last n characters from a given string. The string length must be greater or equal to n.</title>
</head>
<body>

</body>
</html>

JavaScript Code:

function two_string(str, n)
  {
    first_part = str.substring(0, n);
    last_part = str.substring(str.length - n);
    return first_part + last_part;
 }

console.log(two_string("JavaScript", 2));
console.log(two_string("JavaScript", 3));

Sample Output:

Japt
Javipt

Flowchart:

Flowchart: JavaScript - Create a new string 
  taking the first and last n characters from a given string

ES6 Version:

function two_string(str, n)
  {
    first_part = str.substring(0, n);
    last_part = str.substring(str.length - n);
    return first_part + last_part;
 }

console.log(two_string("JavaScript", 2));
console.log(two_string("JavaScript", 3));

Live Demo:

See the Pen Create a new string taking the first and last n characters from a given string by w3resource (@w3resource) on CodePen.


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Previous: Write a JavaScript program to create a new string from a given string, removing the first and last characters of the string if the first or last character are 'P'.
Next: Write a JavaScript program to compute the sum of three elements of a given array of integers of length 3.

What is the difficulty level of this exercise?



JavaScript: Tips of the Day

Parameter's value

function getItems(fruitList, ...args, favoriteFruit) {
  return [...fruitList, ...args, favoriteFruit]
}

getItems(["banana", "apple"], "pear", "orange")

...args is a rest parameter. The rest parameter's value is an array containing all remaining arguments, and can only be the last parameter! In this example, the rest parameter was the second parameter. This is not possible, and will throw a syntax error.

function getItems(fruitList, favoriteFruit, ...args) {
  return [...fruitList, ...args, favoriteFruit];
}


getItems(['banana', 'apple'], 'pear', 'orange');
The above example works. This returns the array [ 'banana', 'apple', 'orange', 'pear' ].

Ref: https://bit.ly/3jFRBje