What is the best way to confirm that my TypeScript string contains exactly two words?

Question

What is the best way to confirm that my TypeScript string contains exactly two words?

Can you provide guidance on how to validate that a string contains exactly two words using TypeScript?

I'm looking to implement this validation in order to ensure that I only call the server if the name is in "first last" format.

javascript typescript

Answer 1

Answer №1

The solution doesn't rely on TypeScript; it's fundamental JavaScript.

To check for a specific pattern within a string, you can utilize a regular expression like this:

function testPattern(input){
 // Check if the input contains letters (any number and any case)
 // followed by one space and then more letters (any number and any case).
 // You can easily modify the regex to account for different cases or character counts if needed.
 return /^[A-Za-z]+ [A-Za-z]+$/.test(input);
}

console.log(testPattern("Scott"));
console.log(testPattern("Scott Marcus"));
console.log(testPattern("Scott\nMarcus"));

Answer 2

The solution doesn't rely on TypeScript; it's fundamental JavaScript.

To check for a specific pattern within a string, you can utilize a regular expression like this:

function testPattern(input){
 // Check if the input contains letters (any number and any case)
 // followed by one space and then more letters (any number and any case).
 // You can easily modify the regex to account for different cases or character counts if needed.
 return /^[A-Za-z]+ [A-Za-z]+$/.test(input);
}

console.log(testPattern("Scott"));
console.log(testPattern("Scott Marcus"));
console.log(testPattern("Scott\nMarcus"));

Answer 3

Answer №2

When working with TypeScript, certain things cannot be directly typed, however, you can utilize type guards to specify that a parameter value must pass a specific test before being considered a valid input for a function.

Below is an example of how Scott's answer could be implemented in a "strongly typed" manner:

my-custom-types.d.ts

// A supertype for strings that have passed a RegEx test
declare type TwoWords = Branded<string, 'two-words'>

// Defines a unique primitive type as nominal types are not yet supported
// @see https://github.com/Microsoft/TypeScript/issues/202
declare type Branded<T, U> = T & { '__brand': U }

// Represents a full name in "first last" format
declare type FullName = TwoWords

my-test.ts

// Type guard that converts strings with two words to TwoWords type
function isTwoWords(input: string): input is TwoWords {
    return /^[A-Za-z]+ [A-Za-z]+$/.test(input)
}

// Function that should only receive strings with two words 
function showName(name: FullName) {
    let [first, last] = name.split(' ') // Can safely split the name
    console.log(`${last}, ${first}`)
}

let name1 = 'John'
let name2 = 'John Doe'
let name3 = 'John Doe Junior'

// Error, attempting to pass a string with unknown word count
showName(name2)

for (let name of [name1, name2, name3]) {
    if (isTwoWords(name)) {
        // No errors, TS ensures only a TwoWords type reaches this point
        showName(name)
    }
}

Answer 4

When working with TypeScript, certain things cannot be directly typed, however, you can utilize type guards to specify that a parameter value must pass a specific test before being considered a valid input for a function.

Below is an example of how Scott's answer could be implemented in a "strongly typed" manner:

my-custom-types.d.ts

// A supertype for strings that have passed a RegEx test
declare type TwoWords = Branded<string, 'two-words'>

// Defines a unique primitive type as nominal types are not yet supported
// @see https://github.com/Microsoft/TypeScript/issues/202
declare type Branded<T, U> = T & { '__brand': U }

// Represents a full name in "first last" format
declare type FullName = TwoWords

my-test.ts

// Type guard that converts strings with two words to TwoWords type
function isTwoWords(input: string): input is TwoWords {
    return /^[A-Za-z]+ [A-Za-z]+$/.test(input)
}

// Function that should only receive strings with two words 
function showName(name: FullName) {
    let [first, last] = name.split(' ') // Can safely split the name
    console.log(`${last}, ${first}`)
}

let name1 = 'John'
let name2 = 'John Doe'
let name3 = 'John Doe Junior'

// Error, attempting to pass a string with unknown word count
showName(name2)

for (let name of [name1, name2, name3]) {
    if (isTwoWords(name)) {
        // No errors, TS ensures only a TwoWords type reaches this point
        showName(name)
    }
}

Answer 5

Answer №3

Using Regular Expressions, you can validate a string to ensure it contains two words, possibly with accents, hyphens, and apostrophes.

const allowedChars = "a-z\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF"; // Reference: https://stackoverflow.com/a/1073545/188246
const isTwoWordNameRegEx = new RegExp(`^[${allowedChars}]+(['\-][${allowedChars}]+)* [${allowedChars}]+(['\-][${allowedChars}]+)*$`, "i");

isTwoWordNameRegEx.test("Sébastien Doe");         // true
isTwoWordNameRegEx.test("John Doe");              // true
isTwoWordNameRegEx.test("John Doe-Williams")      // true
isTwoWordNameRegEx.test("Scarlett O'Hara")        // true
isTwoWordNameRegEx.test("John Doe-Williams-Jane") // true
isTwoWordNameRegEx.test("John Doe-")              // false
isTwoWordNameRegEx.test("John Doe'")              // false
isTwoWordNameRegEx.test("John' Doe")              // false
isTwoWordNameRegEx.test("John Doe Williams")      // false

However, it's important to note that assumptions about names are not always accurate. Refer to Falsehoods Programmers Believe About Names for more information.

If you still wish to restrict it to two words, consider a relaxed version of the regex pattern:

const isTwoWordNameRegEx = /^\S+ \S+$/;

Answer 6

Using Regular Expressions, you can validate a string to ensure it contains two words, possibly with accents, hyphens, and apostrophes.

const allowedChars = "a-z\u00A0-\uD7FF\uF900-\uFDCF\uFDF0-\uFFEF"; // Reference: https://stackoverflow.com/a/1073545/188246
const isTwoWordNameRegEx = new RegExp(`^[${allowedChars}]+(['\-][${allowedChars}]+)* [${allowedChars}]+(['\-][${allowedChars}]+)*$`, "i");

isTwoWordNameRegEx.test("Sébastien Doe");         // true
isTwoWordNameRegEx.test("John Doe");              // true
isTwoWordNameRegEx.test("John Doe-Williams")      // true
isTwoWordNameRegEx.test("Scarlett O'Hara")        // true
isTwoWordNameRegEx.test("John Doe-Williams-Jane") // true
isTwoWordNameRegEx.test("John Doe-")              // false
isTwoWordNameRegEx.test("John Doe'")              // false
isTwoWordNameRegEx.test("John' Doe")              // false
isTwoWordNameRegEx.test("John Doe Williams")      // false

However, it's important to note that assumptions about names are not always accurate. Refer to Falsehoods Programmers Believe About Names for more information.

If you still wish to restrict it to two words, consider a relaxed version of the regex pattern:

const isTwoWordNameRegEx = /^\S+ \S+$/;

What is the best way to confirm that my TypeScript string contains exactly two words?

Answer №1

Answer №2

Answer №3

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