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typescript discriminated union

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YOU.com answered on April 24, 2021 Popularity 9/10 Helpfulness 4/10

answer typescript discriminated union

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typescript discriminated union

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// Example of a discriminated union in TypeScript
interface Square {
  kind: "square";
  sideLength: number;
}

interface Circle {
  kind: "circle";
  radius: number;
}

type Shape = Square | Circle;

function calculateArea(shape: Shape): number {
  switch (shape.kind) {
    case "square":
      return shape.sideLength ** 2;
    case "circle":
      return Math.PI * shape.radius ** 2;
    default:
      throw new Error("Invalid shape");
  }
}

const square: Square = {
  kind: "square",
  sideLength: 5
};

const circle: Circle = {
  kind: "circle",
  radius: 3
};

console.log(calculateArea(square)); // Output: 25
console.log(calculateArea(circle)); // Output: 28.274333882308138

Popularity 9/10 Helpfulness 4/10 Language typescript

Source: Grepper

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Contributed on Sep 12 2023

YOU.com

0 Answers Avg Quality 2/10

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typescript discriminated unions

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// Object unions with variants of a similiar property, but different
// key names. Need to add a common property to connect them.
interface Circle {
  kind: "circle";
  radius: number;
}
 
interface Square {
  kind: "square";
  sideLength: number;
}
 
type Shape = Circle | Square;

// TypeScript can now narrow out the members
function getArea (shape: Shape) {
  if (shape.kind === "circle") {
    return Math.PI * shape.radius ** 2 // safely accessing shape.radius
  }
}

// Alternatively use a switch statement
switch(shape.kind) {
  case 'circle':
    return Math.PI * shape.radius ** 2
  case 'square':
    return shape.sideLength ** 2

Popularity 9/10 Helpfulness 2/10 Language typescript

Source: Grepper

Tags: typescript t

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Contributed on Jun 10 2022

Stupid Scarab

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typescript union

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// Union Type: function reacts depending on x type (array of string OR string)
function welcomePeople(x: string[] | string) {
  if (Array.isArray(x)) {
    console.log("Hello, " + x.join(" and "));  		// 'x' is 'string[]'
  } else {										
    console.log("Welcome lone traveler " + x);		// 'x' is 'string'
  }
}

Popularity 10/10 Helpfulness 1/10 Language typescript

Source: www.typescriptlang.org

Tags: typescript t

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Contributed on Apr 24 2021

VasteMonde

0 Answers Avg Quality 2/10

typescript union

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type Circle = { kind: 'circle'; radius: number };
type Rect = { kind: 'rect'; width: number; height: number };
type Shape = Circle | Rect;

function getArea(shape: Shape) {
    return shape.kind === 'circle' ? 
        Math.PI * shape.radius ** 2
        : shape.width * shape.height;
}

Popularity 10/10 Helpfulness 1/10 Language typescript

Source: dev.to

Tags: typescript t

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Contributed on Jan 10 2023

haya huang

0 Answers Avg Quality 2/10

typescript discriminated union

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