Types in TypeScript : any Type

typescript
Published on March 3, 2021

The any type in TypeScript represents a data-type that can hold any possible value. any is similar to Javascript variables where no type checking is performed and they can hold any value.

// x is of type "any"
let x: any;

// all valid as no type checking involved
x = 4;
x = "Hello World";
x = { id: 1001 };

any declares to TypeScript that we know more about the type of the data and that TypeScript should trust it.

Other FAQs

  • Variables of type any can be used to bypass type checking and basically behave like plain Javascript variables. In Javascript there is no type checking and variables can hold any value.
  • Variables of type any can allow properties & methods to be accessed even if they are not existing. TypeScript trusts that the code is safe and throws no error.

    let x: any = 4;
    
    // no error
    x.length;
    
    // no error
    x.someMethod();
    
  • Variables of type any can be assigned to variables of other types. Again TypeScript trusts that this would be safe.

    let x: any = "Hello World";
    
    let a: number = 5;
    
    // allowed
    a = x;
    
  • Since any bypasses type checking, this defeats the very purpose of using TypeScript. any should be used as the last resort, in cases like interacting with third party Javascript libraries where we are not sure about the type of the data being returned.
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