@threestup/monads
v1.1.0
Published
Option and Result types for JavaScript; TypeScript first
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1,015
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Type safe Option and Result type
Inspired by Rust.
Previously known on npm as tsp-monads.
NOTE: Works with TypeScript 2+ and JavaScript (ES6+). strictNullChecks
option / flag strongly recommended.
Documentation
Install
npm install @threestup/monads
Basic Usage
import { Option, Some, None } from '@threestup/monads'
const divide = (numerator: number, denominator: number): Option<number> => {
if (denominator === 0) {
return None
} else {
return Some(numerator / denominator)
}
};
// The return value of the function is an option
const result = divide(2.0, 3.0)
// Pattern match to retrieve the value
const message = result.match({
some: res => `Result: ${res}`,
none: 'Cannot divide by 0',
})
console.log(message) // 'Result: 0.6666666666666666'
import { Result, Ok, Err } from '@threestup/monads'
function getIndex(values: string[], value: string): Result<number, string> {
const index = values.indexOf(value)
switch (index) {
case -1:
return Err('Value not found')
default:
return Ok(index)
}
}
console.log(getIndex(['a', 'b', 'c'], 'b')) // Ok(1)
console.log(getIndex(['a', 'b', 'c'], 'z')) // Err('Value not found')
...