Parameter 'X' implicitly has an 'any' type in TypeScript

# Parameter 'X' implicitly has an 'any' type in TypeScript

The "Parameter 'X' implicitly has an 'any' type" error occurs when a function's parameter has an implicit type of any.

To solve the error, explicitly set the parameter's type to any, use a more specific type or set noImplicitAny to false in tsconfig.json.

Here is an example of how the error occurs.

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// ⛔️ Error: Parameter 'a' implicitly has an 'any' type.ts(7006)
function sum(a, b) {
  return a + b;
}

The parameters of the sum function are not explicitly typed, so TypeScript set them to have an implicit type of any.

# Explicitly setting the type of the parameters to any

One way to solve the error is to explicitly set the type of the parameters to any.

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function sum(a: any, b: any) {
  return a + b;
}

console.log(sum(10, 50)); // 👉️ 60

The same approach can be used with arrow functions, callbacks, etc.

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const sum = (a: any, b: any) => {
  return a + b;
};

console.log(sum(10, 50)); // 👉️ 60

Here is an example that sets the parameter of a callback function to have a type of any.

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const arr = ['bobby', 'hadz', 'com'];

arr.forEach((item: any) => {
  console.log(item);
});

This isn't necessary in this particular case because TypeScript is sometimes able to infer the type of a variable.

However, if the arr variable is implicitly typed as any, then its items will also have an implicit type of any which would cause the error.

You might also have to turn off type checking for event handler functions, e.g. in Angular.

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function handleClick(event: any) {
  console.log(event);
}

# Type the function's parameters accordingly

A much better solution is to be more specific when setting the type of the parameters.

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function sum(a: number, b: number) {
  return a + b;
}

console.log(sum(10, 50)); // 👉️ 60

Now the parameters in the sum function are explicitly typed to be numbers.

If you need to declare a function with a variable number of arguments, click on the following article.

# Suppressing the error for your entire project

If you don't like this behavior and want to suppress errors when values are implicitly typed as any, set the noImplicitAny option to false in your tsconfig.json file.

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{
  "compilerOptions": {
    // ... other properties
    "noImplicitAny": false
  }
}

If the strict property is set to true, the noImplicitAny option defaults to true.

When TypeScript can't find type annotations for a value and they can't be inferred, it falls back to a type of any.

By turning it off, you suppress the error messages. However, the more strictly you write your TypeScript code, the less likely you are to get unexpected runtime errors.

You can also use a comment to disable type checking.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Setting optional parameters in Functions or Classes in TS
• Declare a function with a Promise return type in TypeScript
• How to Declare a Function that throws an Error in TypeScript
• 'this' implicitly has type 'any' error in TypeScript [Fixed]