Convert String to int in JavaScript

The world of programming often involves mixing data types. Sometimes, you'll have a number represented as a string (like "123"), but you need to perform mathematical operations on it. This is where string-to-integer conversion becomes essential.

I remember back when I was first learning JavaScript, I ran into a common problem: figuring out how to get my code to treat numbers pulled from user input as actual numbers, and not just text. Turns out, converting between integers and strings is a frequent task with some interesting ways to go about it!

Let us learn how to convert string to int in javascript with different methods and why it is important to do so in this tutorial.

Why Convert string to int in JavaScript?

Forms on websites often collect numbers as text within input fields. To calculate or manipulate this data, you'll need them as true numbers. Also, when working with data received from files, databases, or other sources, numbers might be accidentally stored as strings.

Strings representing numbers won't behave as expected in calculations ("10" + "10" would become "1010" as strings!).

The Importance of Type Conversion

JavaScript is loosely typed, meaning a variable can hold any type of data (string, number, boolean, etc.) and its type can change dynamically. However, different operations often expect specific data types.

To ensure your code behaves as expected, you'll often need to explicitly convert between types. Failing to do so might lead to unexpected concatenation instead of addition, or other subtle errors. Also, when interacting with external systems, databases, or user input, you might need to convert the data you receive into the appropriate types for your code to process it effectively.

JavaScript will try to be helpful and implicitly convert types in some cases, but this can lead to surprises. Explicitly managing data types puts you in control. Especially when dealing with external data, it's wise to validate input and handle potential cases where a string might not be in the expected format before attempting conversion.

Numeric Strings vs. Non-Numeric Strings

Let us learn the core differences between numeric strings and non-numeric strings.

Numeric Strings

These strings contain only characters that represent a valid number (e.g., "15", "-25.8", even "0012" is valid though will be treated as 12). Numeric strings may include an optional leading plus (+) or minus (-) sign. They may also include a decimal point and fractional digits for floating-point representation.

Non-Numeric Strings

Non-numeric strings contain any other characters that don't form a valid numerical representation.

Examples: "hello", "25abc", "12.3.4" (multiple decimal points)

How to Convert string to int in JavaScript?

1. parseInt()

parseInt() is your primary tool for extracting integers from strings. It parses the string from left to right. If it encounters a non-numeric character, it stops and returns the integer parsed up to that point. parseInt() ignores trailing whitespace after the number.

Always provide the radix for non-decimal conversions, or you'll get unexpected results.

If the string doesn't start with a number, parseInt() returns NaN (Not a Number). You'll likely want to check for this.

The radix parameter: This critical parameter tells parseInt() which numerical base to use. The default is 10 (decimal). For other bases (e.g., binary, hexadecimal), specify the radix as the second argument: parseInt('10110', 2); // Binary conversion

Example:

2. Number()

Number() is a constructor function, more versatile than parseInt(). It attempts to convert the string into a number, potentially a floating-point number if the string contains a decimal.

If the string is not a valid number in any form, it returns NaN. Choose Number() if you're potentially dealing with floating-point numbers, or you're confident your string represents a valid (potentially decimal) number.

Example:

3. Unary Plus Operator (+)

Placing a + in front of a numeric string is a shorthand way to coerce it into a number. Less explicit than other methods, potentially making your code less readable to others. It only handles the same conversions as Number(). If the string is invalid, it returns NaN.

Example:

Advanced Considerations

Let us discuss some advanced considerations that must be studied when we are trying to convert string to int in JavaScript.

Handling Non-Numeric Strings and Error Detection

The isNaN() (stands for Is Not a Number) function is indispensable for checking the output of conversion methods.

Example:

Floating-Point Numbers

If the string may contain a decimal point, parseFloat() is needed to preserve the complete numeric value.

Example:

Base/Radix Handling

The parseInt() function's second parameter (the radix) specifies the number base to use during conversion. The default is decimal (base-10).

Common radixes:

• Decimal (base-10): The everyday number system
• Binary (base-2): Used in computer representation (0 and 1)
• Hexadecimal (base-16): Uses 0-9 and A-F for more compact representation

Example:

If you wish to master essential JS concepts like the JavaScript DOM functions, you can enroll in any of the full stack development courses by upGrad.

Best Practices and Choosing the Right Method

Here are the decision factors for string to int javascript conversion:

1. String Format: Are you expecting clean numeric strings ("123"), or could they contain non-numeric characters ("123hello") or decimals ("45.6")?
2. Error Handling: Do you need strict conversion that produces an error when non-numeric characters are present, or do you want more flexibility to extract just the numeric portion?
3. Desired Behavior: Do you want only the integer portion, or should it handle potential decimal values as well?

Convert string to int in JS code examples and comparisons:

Best Practices

Here are some best practices for JavaScript int to string conversion:

• For the most control and strict conversion, parseInt() is generally preferred due to its radix parameter.
• Use isNaN() to validate the result of a conversion before using it.
• If handling decimals is essential, use Number() or parseFloat().

Choosing the Right Method

Here is a table for determining the right method for each scenario:

JS convert int to string Examples

As a bonus for sticking with me for so long in this tutorial, I will quickly take you through converting int back to string in case you need it for experimenting with Java Script string to int. Let us check out some JavaScript convert string to int examples.

toString() Method

The most straightforward approach. It's a built-in method that all numbers have.

Example:

String() Constructor

A more general way to convert values to strings.

Example:

Template Literals (Backticks)

Modern and convenient for embedding variables into strings.

Example:

Choosing the Right Method

toString() is usually the easiest and clearest for converting just numbers. String() is handy if you might be converting mixed data types to strings. Template literals shine when creating longer strings with interpolated variables.

Let's Practice!

Imagine you have these variables:

Tasks:

• Convert each to a string using a different method.
• Create a template literal that says: "The score is 56, located in ZIP code 90210. Approximate pi value: 3.14"

Wrapping Up

When we want to convert string to number in JavaScript, be mindful of floating-point numbers when precision beyond integers is necessary. Also, careful error handling prevents unexpected behavior in your code. The radix parameter gives you control when working with different number systems.

If you wish to master technologies such as JavaScript, you can enroll in upGrad’s software engineering courses.

Frequently Asked Questions

1. How to convert a string to integer in JS?
Use the parseInt() function to convert int to string JavaScript. For more accurate results, the string should start with a numeric representation.

2. How to convert a string to int?
You can use the parseInt() function to convert string to integer JS.

3. How to check if string can be converted to int JavaScript?
Use the isNaN() function in combination with parseInt(). If isNaN(parseInt(yourString)) returns true, the string can't be reliably converted to an integer.

4. How to get only int value from string in JavaScript?
Use parseInt() to extract the leading integer from a string. If the string contains other characters, parseInt() will stop parsing when it encounters a non-numeric character.

5. How to convert string to int without using parseInt JavaScript?
You can use the number() constructor which carries out JavaScript convert string to integer (integer or float if decimals are present). You can also use the unary plus operator (+) which converts string to a number type.

6. How to convert to a string JavaScript?
Use the toString() method to convert various JavaScript data types into strings. For example: myNumber.toString().