How to Trim Leading Zeros from a String in JavaScript

Jun 22, 2021

We recommend using regular expressions and the string replace() method to remove leading zeros from a string.

let x = '0042';
x = x.replace(/^0+/, '');

x; // '42';
typeof x; // 'string'

Converting to a Number

You may have seen code that uses x * 1 or +x to remove leading zeros from a string. This approach works for basic cases, with the key difference that you end up with a number rather than a string.

let x = '0042';
x = parseInt(x);

x; // 42
typeof x; // 'number'

let y = '007';
y = +y;
y; // 7
typeof y; // 'number'

However, things get tricky with strings that contain hex, octal, and binary literals as shown below.

let x = '0xFF';
x = +x;
x; // 255

Whether this behavior is correct depends on your use case. However, if you want to treat x as a string and remove leading zeros, the correct output here would be 'xFF'. In that case, using + or parseInt() won't work. You can tell parseInt() to always use base 10 and avoid parsing strings that start with 0x as hexadecimal numbers, but then you end up with a 0.

let x = '0xFF';
x = parseInt(x, 10);

x; // 0, because `parseInt()` parses as much as it can
typeof x; // 'number'

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