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How to remove the last digit of a number and execute the remaining digits in JavaScript?
In JavaScript, you can remove the last digit from a number using different approaches. The most common methods involve string manipulation or mathematical operations like bitwise operations.
When working with numbers, you typically need to convert the number to a string to use string methods, or use mathematical operations to avoid type conversion altogether.
Method 1: Using String substring()
The substring() method extracts characters from a string between two specified indices.
Syntax
str.substring(startIndex, endIndex)
To remove the last digit, use str.substring(0, str.length - 1) where the first parameter is the starting index (0) and the second is the ending index (length - 1).
<!DOCTYPE html>
<html>
<head>
<title>Remove Last Digit Using substring()</title>
</head>
<body>
<script>
var num1 = 2345;
let str = num1.toString();
var result = str.substring(0, str.length - 1);
document.write("Original number: " + num1 + "<br>");
document.write("After removing last digit: " + result);
</script>
</body>
</html>
Original number: 2345 After removing last digit: 234
Method 2: Using Bitwise OR Operation
The bitwise OR operation with 0 truncates decimal places. When you divide a number by 10 and apply | 0, it removes the last digit without string conversion.
<!DOCTYPE html>
<html>
<head>
<title>Remove Last Digit Using Bitwise OR</title>
</head>
<body>
<script>
document.write("2345 ? " + ((2345 / 10) | 0) + "<br>");
document.write("23456 ? " + ((23456 / 10) | 0) + "<br>");
document.write("234567 ? " + ((234567 / 10) | 0) + "<br>");
document.write("2345678 ? " + ((2345678 / 10) | 0) + "<br>");
document.write("23456789 ? " + ((23456789 / 10) | 0));
</script>
</body>
</html>
2345 ? 234 23456 ? 2345 234567 ? 23456 2345678 ? 234567 23456789 ? 2345678
Method 3: Processing Array Elements
You can apply the same logic to remove the last digit from multiple numbers in an array.
<!DOCTYPE html>
<html>
<head>
<title>Remove Last Digit from Array Elements</title>
</head>
<body>
<script>
var array = [23, 45, 56, 67, 78];
var results = [];
document.write("Original array: [" + array.join(", ") + "]<br>");
document.write("After removing last digits: [");
for (let i = 0; i < array.length; i++) {
const element = ((array[i] / 10) | 0);
results.push(element);
document.write(element);
if (i < array.length - 1) document.write(", ");
}
document.write("]");
</script>
</body>
</html>
Original array: [23, 45, 56, 67, 78] After removing last digits: [2, 4, 5, 6, 7]
Method 4: Using Math.floor()
An alternative mathematical approach uses Math.floor() to achieve the same result.
<!DOCTYPE html>
<html>
<head>
<title>Remove Last Digit Using Math.floor()</title>
</head>
<body>
<script>
var numbers = [1234, 5678, 9012];
for (let i = 0; i < numbers.length; i++) {
var original = numbers[i];
var result = Math.floor(original / 10);
document.write(original + " ? " + result + "<br>");
}
</script>
</body>
</html>
1234 ? 123 5678 ? 567 9012 ? 901
Comparison
| Method | Type Conversion | Performance | Readability |
|---|---|---|---|
| substring() | Required | Slower | High |
| Bitwise OR (| 0) | Not required | Faster | Medium |
| Math.floor() | Not required | Fast | High |
Conclusion
The bitwise OR method (num / 10) | 0 is the most efficient for removing the last digit, while substring() offers better readability. Choose based on your performance needs and code clarity preferences.
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