.parseInt()

Published May 31, 2024
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In JavaScript, the .parseInt() function converts a string into an integer. This function parses a string argument and returns an integer of the specified radix (the base in mathematical numeral systems).

Syntax

Number.parseInt(string, radix);
  • Number: The JavaScript built-in object that serves as a namespace for numerical-related functions and constants.
  • string: The string to be parsed. The leading whitespace in the string is ignored.
  • radix: An optional parameter that specifies the base of the numeral system to be used for parsing. It is an integer between 2 and 36. If not provided, the radix defaults to 10, except when the string starts with 0x or 0X, which indicates a hexadecimal number.

Example

The following example demonstrates some of the use cases of the .parseInt() function:

// converting string to decimal
const x = Number.parseInt('100');
console.log(x);
// converting binary to decimal
const y = Number.parseInt('101', 2);
console.log(y);
//converting hexadecimal to decimal
const z = Number.parseInt('7F', 16);
console.log(z);
// unintended uses of parseInt() function:
// radix must be between 2 and 36 inclusive
const invalidRadix = Number.parseInt('123', 1);
console.log(invalidRadix);
// first character of string must be a numeric digit
const firstChar = Number.parseInt('*123');
console.log(firstChar);

The above code will give the following output:

100
5
127
NaN
NaN

Note: The above example does not cover all possible situations or options. They are just a few examples that help illustrate the concept.

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