JavaScript: Reverse a number
JavaScript Function: Exercise-1 with Solution
Write a JavaScript function that reverse a number.
Sample Data and output:
Example x = 32243;
Expected Output: 34223
Pictorial Presentation:
Sample Solution:
HTML Code:
<!DOCTYPE html>
<html>
<head>
<meta charset=utf-8 />
<title>Reverse a number</title>
</head>
<body>
</body>
</html>
JavaScript Code:
function reverse_a_number(n)
{
n = n + "";
return n.split("").reverse().join("");
}
console.log(Number(reverse_a_number(32243)));
Sample Output:
34223
Explanation:
Assume n = 1000.
Convert a number to a string :
Code :
-> n = n + "";
Note : There are different ways to convert number to string :
- String literal -> str = "" + num + "";
- String constructor -> str = String(num);
- toString -> str = num.toString();
- String Literal simple -> str = "" + num;
The split() method is used to split a String object into an array of strings by separating the string into substrings.
Code :
console.log('1000'.split(""));
Output : ["1", "0", "0", "0"]
The reverse() method is used to reverse an array in place. The first array element becomes the last and the last becomes the first.
Code : console.log(["1", "0", "0", "0"].reverse());
Output : ["0", "0", "0", "1"]
The join() method is used to join all elements of an array into a string.
Code : console.log(["1", "0", "0", "0"].reverse().join(""));
The Number constructor contains constants and methods for working with numbers. Values of other types can be converted to numbers using the Number() function.
Output : 1
Flowchart:
Live Demo:
See the Pen JavaScript -Reverse a number-function-ex- 1 by w3resource (@w3resource) on CodePen.
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Previous: Write a JavaScript program to find the smallest prime number strictly greater than a given number.
Next: Write a JavaScript function that checks whether a passed string is palindrome or not?
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JavaScript: Tips of the Day
How to insert an item into an array at a specific index (JavaScript)?
What you want is the splice function on the native array object.
arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:
var arr = []; arr[0] = "Jani"; arr[1] = "Hege"; arr[2] = "Stale"; arr[3] = "Kai Jim"; arr[4] = "Borge"; console.log(arr.join()); arr.splice(2, 0, "Lene"); console.log(arr.join());
Ref: https://bit.ly/2BXbp04
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