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How to convert a string of any base to an integer in JavaScript?
An integer can be represented in various formats in programming languages such as Binary (base 2), Decimal (base 10), Hexadecimal (base 16), and Octal (base 8). A Binary number consists of two digits only (0 & 1), whereas a decimal consists of digits from 0 to 9.
We can convert a string to an integer using the parseInt() method. When the integer is represented in a different base, we need to pass the base parameter to decode it correctly.
Syntax
parseInt(string_value, base) parseInt(string_value) // Defaults to base 10
Parameters
- string_value: The string to convert to an integer
- base (optional): The base of the number system (2-36). Defaults to 10
Return Value
Returns an integer parsed from the string, or NaN if the string cannot be parsed.
Example 1: Converting Without Base Parameter
When no base is specified, parseInt() defaults to base 10 (decimal):
<!DOCTYPE html>
<html>
<head>
<title>String to Integer Conversion</title>
</head>
<body>
<h2 style="color:green">Welcome To Tutorials Point</h2>
<script>
let stringConversion = (string_value) => {
console.log("Initial Type: " + typeof string_value);
let integer_value = parseInt(string_value);
console.log("Final Type: " + typeof integer_value);
console.log("Result: " + integer_value);
console.log("---");
};
stringConversion("8475628");
stringConversion("101010");
stringConversion("0x3278"); // Hexadecimal prefix
</script>
</body>
</html>
Initial Type: string Final Type: number Result: 8475628 --- Initial Type: string Final Type: number Result: 101010 --- Initial Type: string Final Type: number Result: 12920
Example 2: Converting With Different Base Values
Here we specify different bases to convert strings from various number systems:
<!DOCTYPE html>
<html>
<head>
<title>Base Conversion Example</title>
</head>
<body>
<h2 style="color:green">Welcome To Tutorials Point</h2>
<script>
let baseConversion = (string_value, base) => {
console.log("String: " + string_value + ", Base: " + base);
let integer_value = parseInt(string_value, base);
console.log("Integer value: " + integer_value);
console.log("---");
};
baseConversion("101010", 2); // Binary to decimal
baseConversion("101", 10); // Decimal to decimal
baseConversion("256472", 8); // Octal to decimal
baseConversion("FF", 16); // Hexadecimal to decimal
</script>
</body>
</html>
String: 101010, Base: 2 Integer value: 42 --- String: 101, Base: 10 Integer value: 101 --- String: 256472, Base: 8 Integer value: 89914 --- String: FF, Base: 16 Integer value: 255
Common Base Systems
| Base | System | Digits Used | Example |
|---|---|---|---|
| 2 | Binary | 0, 1 | "1010" ? 10 |
| 8 | Octal | 0-7 | "12" ? 10 |
| 10 | Decimal | 0-9 | "10" ? 10 |
| 16 | Hexadecimal | 0-9, A-F | "A" ? 10 |
Key Points
-
parseInt()stops parsing when it encounters an invalid character - Base parameter must be between 2 and 36
- Returns
NaNif the string cannot be parsed - Leading whitespace is ignored
Conclusion
Use parseInt(string, base) to convert strings from any number system to decimal integers. The base parameter is essential when working with non-decimal number systems like binary, octal, or hexadecimal.
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