How to pad a string to get the determined length using JavaScript ?
In this article, we will pad a string to get the determined length using JavaScript. To achieve this we have a few methods in javascript which are described below:
Methods to pad a string to get the determined length:
Table of Content
- Method 1: Using the padStart() method.
- Method 2: Custom function using repeat() and slice() method.
- Method 3: Using JavaScript loops
- Method 4: Using the padEnd() method.
Method 1: Using the padStart() method.
The padStart() method can be used to pad a string with the specified characters to the specified length. It takes two parameters, the target length, and the string to be replaced with. The target length is the length of the resulting string after the current string has been padded. The second parameter is the characters that the string would be padded. If a number is to be padded, it has to be first converted into a string by passing it to the String constructor. Then the padStart() method is used on this string.
Syntax:
String(strToPad).padStart(padLength, padChar)
Example: This example uses the above approach to pad a string.
function pad() {
// Input string
example1 = "abcdefg";
example2 = 1234;
// Display input string
console.log(example1);
console.log(example2);
// Padded string
prepended_out = String(example1).padStart(10, '*');
prepended_out2 = String(example2).padStart(10, '^#');
// Display output
console.log(prepended_out);
console.log(prepended_out2);
}
// Function Cal
pad();
Output
abcdefg 1234 ***abcdefg ^#^#^#1234
Method 2: Custom function using repeat() and slice() method.
The string.repeat() is an inbuilt method in JavaScript that is used to build a new string containing a specified number of copies of the string on which this method has been called.
Syntax:
string.repeat(count);
The Javascript arr.slice() method returns a new array containing a portion of the array on which it is implemented. The original remains unchanged.
Syntax:
arr.slice(begin, end)
Example: This example uses the above approach to pad a string.
function padStr(padChar, padLength, originalString) {
// Convert the pad character and original
// string to String
padChar = String(padChar);
originalString = String(originalString);
// Calculate the length of padding characters
padLeft = padLength - originalString.length;
// Create the pad string
padString = padChar.repeat(padLeft);
// Add the pad string to the original string
// slice it to the padLength if it exceeds
// the pad length specified
newString = (padString +
originalString).slice(-padLength);
return newString;
}
function pad() {
// Input string
example1 = "abcdefg";
example2 = 1234;
// Display input
console.log(example1);
console.log(example2);
// Padded string
prepended_out = padStr('*', 10, example1);
prepended_out2 = padStr('^#', 10, example2);
// Display output
console.log(prepended_out);
console.log(prepended_out2);
}
// Function Cal
pad();
Output
abcdefg 1234 ***abcdefg ^#^#^#1234
Method 3: Using JavaScript loops
A while loop is a control flow statement that allows code to be executed repeatedly based on a given Boolean condition. The while loop can be thought of as a repeating if statement.
Syntax :
while (boolean condition) {
loop statements...
}
Example:
function padStr(padChar, padLength, originalString) {
newString = originalString;
// Loop until desired length is reached
while (newString.length < padLength) {
// Add padChar each time
paddedString = padChar + paddedString;
}
return newString;
}
function pad() {
// Input string
example1 = "abcdefg";
example2 = 1234;
console.log(example1);
console.log(example2);
// Padded string
prepended_out = String(example1).padStart(10, '*');
prepended_out2 = String(example2).padStart(10, '^#');
// Display output
console.log(prepended_out);
console.log(prepended_out2);
}
// Function Cal
pad();
Output
abcdefg 1234 ***abcdefg ^#^#^#1234
Method 4: Using the padEnd() method.
The padEnd() method pads the current string with another string (multiple times, if needed) until the resulting string reaches the given length. The padding is applied from the end (right) of the current string. Similar to padStart(), it takes two parameters: the target length and the pad string.
Example: This example demonstrates how to pad a string using the padEnd() method.
function pad() {
// Input string
let example1 = "abcdefg";
let example2 = 1234;
// Display input string
console.log(example1);
console.log(example2);
// Padded string
let appended_out = String(example1).padEnd(10, '*');
let appended_out2 = String(example2).padEnd(10, '^#');
// Display output
console.log(appended_out);
console.log(appended_out2);
}
// Function Call
pad();
Output
abcdefg 1234 abcdefg*** 1234^#^#^#
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