Borislav Hadzhiev
Sat Oct 23 2021·2 min read
Photo by Sandra Seitamaa
Use the padStart()
method to add leading zeros to a string. The method
allows us to pad the current string with zeros to a specified target length and
returns the result.
function addLeadingZeros(str, targetLength) { return str.padStart(targetLength, '0'); } const str = '53'; console.log(addLeadingZeros(str, 3)); // 053 console.log(addLeadingZeros(str, 4)); // 0053 console.log(addLeadingZeros(str, 5)); // 00053
We used the padStart method to add leading zeros to a string.
We passed the following 2 parameters to the padStart
method:
padStart
method should
return, once it has been padded.0
.An easy way to think about the method is - it pads the original string to a target length with a supplied string.
If you have a string of length 2
and you set the target length to 4
, the
string will get padded with 2 characters.
console.log('22'.padStart(4, '0')); // 👉️ 0022
Here are some more examples of using the padStart
method.
console.log('hello'.padStart(8)); // 👉️ " hello" console.log('hello'.padStart(8, '0')); // 👉️ "000hello" console.log('hello'.padStart(1)); // 👉️ "hello"
In our last example, we provided target length of 1
, which is less than
the string's length. In this scenario, the method returns the string as is.
If the length of the pad string + the length of the original string exceed the specified target lenth, the pad string gets truncated.
console.log('22'.padStart(4, '01234567')); // 👉️ 0122
Our string has a length of 2
and we specified a target length of 4
, so
only 2 of characters from the pad string were prepended to the string.