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This article will discuss excluding properties from a TypeScript type. The exclude property is used to create another type from an existing type with fewer or modified properties.

OmitExclude properties from types in TypeScript

TypeScript allows users to exclude properties from types. Users must use Omitthe type to exclude properties from an existing type.

OmitType creates a new type from an existing type.

grammar:

Omit<Type_Name, 'property'>

example:

type Info = {
    firstName: string,
    lastName: string,
    age: number,
    country: string,
};

type Info1 = Omit<Info, 'country'>;

const info1: Info1 = {
    firstName: 'John',
    lastName: 'Nash',
    age: 27,
};

console.log(info1);

Output:

{
    "firstName": "John",
    "lastName": "Nash",
    "age": 27
}

In the example above, Omita new type is introduced from an existing type using . InfoThe type has four properties, while Info1has three.

We can even Infoimport a new type from an existing type and exclude multiple properties.

example:

type Info = {
    firstName: string,
    lastName: string,
    age: number,
    country: string,
};

type Info1 = Omit<Info, 'country'>;

const info1: Info1 = {
    firstName: 'John',
    lastName: 'Nash',
    age: 27,
};

type Info2 = Omit<Info, 'country' | 'age'>;

const info2: Info2 = {
    firstName: 'Stewen',
    lastName: 'Gold',
};

console.log(info1);
console.log(info2);

Output:

{
    "firstName": "John",
    "lastName": "Nash",
    "age": 27
}
{
    "firstName": "Stewen",
    "lastName": "Gold"
}

As shown above, type Info2is Infoa modified version of type . Note Omithow several properties are excluded from the type.

OmitModify properties in TypeScript using

TypeScript allows users to modify properties. If a user tries to modify Omita type without a type, an error is thrown.

example:

type Info = {
    firstName: string,
    lastName: string,
    age: number,
    country: string,
};

type Info1 = Info & {
    country: {
        countryName: string,
        cityName: string,
    };
};

const info1: Info1 = {
    firstName: 'John',
    lastName: 'Nash',
    age: 27,
    country: {
        countryName: 'China',
        cityName: 'Wuhan',
    },
}

This code has no output because the object info1property countrywill throw an error. The error message is: Type countryName and cityName is not assignable to type string.

To overcome this error, the user must use omittype to modify the type.

example:

type Info = {
    firstName: string,
    lastName: string,
    age: number,
    country: string,
};

type Info1 = Omit<Info, 'country'> & {
    country: {
        countryName: string,
        cityName: string,
    };
};

const info1: Info1 = {
    firstName: 'John',
    lastName: 'Nash',
    age: 27,
    country: {
        countryName: 'China',
        cityName: 'Wuhan'
    },
}

console.log(info1);

Output:

{
    "firstName": "John",
    "lastName": "Nash",
    "age": 27,
    "country": {
        "countryName": "China",
        "cityName": "Wuhan"
    }
}

In the example above, notice Info1that has a modified countrytype. Notice the syntax for updating the property.

Using Omittypes is a good habit to eliminate complexity and increase productivity.