How to remove all zeros from a number string in JavaScript

How to remove all zeros from a number string in JavaScript:

In this post, we will learn how to remove all zeros from a number represented as string in JavaScript. If the string holds only zeros, just return 0. We will learn different ways to solve this problem in this post.

Method 1: By traversing the characters of the string:

This is the naive approach to solve this problem. Traverse the string characters from left to right. If you find any non-zero character, add all characters from this to end to a new result string.

Let’s learn how to do that with an example program:

const removeZeros = (str) => {
    if(str === undefined || str === ''){
        return str;
    }

    let i = 0;

    while(str[i] === '0' && i < str.length){
        i++;
    }

    return i === str.length ? '0' : str.substr(i);
}


let testStrings = ['0000', '', '0', '0012', '001200', '001200120012', 'hello', '0hello0', undefined];

for(let i in testStrings){
    console.log(`${testStrings[i]} ==> ${removeZeros(testStrings[i])}`);
}

Here,

removeZeros function is used to remove all zeros from a given string. It takes a string as the parameter, removes all leading zeros and returns the new string.
If the string is an empty string or undefined, it returns the same string.
- Else, it uses a while loop to iterate over the leading zeros.
If all characters are zero, or if the while loop moves the value of i equal to the string length, it returns 0, else it returns the sub string from i to the end of that string.
testStrings is an array of strings. The for loop iterates through the strings and prints the results for each string.

If you run this program, it will print:

0000 ==> 0
 ==> 
0 ==> 0
0012 ==> 12
001200 ==> 1200
001200120012 ==> 1200120012
hello ==> hello
0hello0 ==> hello0
undefined ==> undefined

As you can see that it removes all leading zeros from the strings. If all are zero, it returns 0.

Method 2: By using replace:

We can also use the replace method. This is an inbuilt method and it can be used to replace all matches by a regular expression by another string. It takes two parameters. The first one is the regular expression to match the characters to replace and the second one is a string to replace the matched values.

If we want to match all the leading zeros of a string, we can pass /^0+/ as the regular expression.

Let’s write down the program:

const removeZeros = (str) => {
    if(str === undefined){
        return str;
    }

    return str.replace(/^0+/, '');
}


let testStrings = ['0000', '', '0', '0012', '001200', '001200120012', 'hello', '0hello0', undefined];

for(let i in testStrings){
    console.log(`${testStrings[i]} ==> ${removeZeros(testStrings[i])}`);
}

That’s only one line. Also, we can remove the check for empty strings from the if statement.

It will print the same result:

0000 ==> 
 ==> 
0 ==> 
0012 ==> 12
001200 ==> 1200
001200120012 ==> 1200120012
hello ==> hello
0hello0 ==> hello0
undefined ==> undefined

JavaScript remove leading zeros example

You can also add few more strings to the array to test with different types of strings.

Method 3: By using parseInt or parseFloat:

If you are sure that the inputs are always integers or floats, you can use these two functions:

parseInt
parseFloat

The parseInt function parses a string argument and returns an integer. Similarly, the parseFloat function parses a string argument and returns a float.

Let’s try parseInt with the same set of strings:

const removeZeros = (str) => {
    return parseInt(str).toString();
}


let testStrings = ['0000', '', '0', '0012', '001200', '001200120012', 'hello', '0hello0', undefined];

for(let i in testStrings){
    console.log(`${testStrings[i]} ==> ${removeZeros(testStrings[i])}`);
}

It will print:

0000 ==> 0
 ==> NaN
0 ==> 0
0012 ==> 12
001200 ==> 1200
001200120012 ==> 1200120012
hello ==> NaN
0hello0 ==> 0
undefined ==> NaN

parseInt will fail for floating point values. We have to use parseFloat:

const removeZeros = (str) => {
    return parseFloat(str).toString();
}


let testStrings = ['00.123', '12.344', '9292.12', 'hello', '12.34hello'];

for(let i in testStrings){
    console.log(`${testStrings[i]} ==> ${removeZeros(testStrings[i])}`);
}

It will work:

00.123 ==> 0
12.344 ==> 12
9292.12 ==> 9292
hello ==> NaN
12.34hello ==> 12

But, if you are not sure about the types of the input strings, you should avoid this method.

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How to remove all zeros from a number string in JavaScript