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What is any type in TypeScript?

Osinachi Chukwujama

The any type in TypeScript is a generic type used when a variable’s type is unknown or when the variable’s type hasn’t yet been defined.

The any type is useful when converting existing JavaScript to TypeScript as it allows one to gradually opt-in and opt-out of type checking during compilation.

Using the any type

The any type should only be used when you don’t want to write a long type just to convince TypeScript that a piece of code is correct. For example:

const config: {
  title: string;
  files: string[];
  options: { preset: string };
} = {
  title: "Some config",
  files: ["file1.js", "file2.js"],
  options: {
    preset: "node-ts",
  },
};

console.log(config)

The any type allows you to shorten the long type declaration, as shown below:

const config: any = {
  title: "Some config",
  files: ["file1.js", "file2.js"],
  options: {
    preset: "node-ts",
  },
};

console.log(config)

Caveat of Using the any type

When you use the any type, you are telling the TypeScript compiler to represent values without any constraints. Therefore, using the any type is like buying a high-end computer and throwing away the RAM – it doesn’t help in many cases.

The code snippet below shows a student object with a name and age property. TypeScript throws an error when you try to access an undefined property like house.

const student = {name: "Harry Potter", age: 12}

console.log(student.house)

When the any type is assigned to the student object, the undefined type checking the advantage is lost. We can access tje undefined properties on the student object as follows:

const student: any = {name: "Harry Potter", age: 12}

console.log(student.house)

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