enforce-unique
enforce-unique is a package that helps you ensure values are unique before you assign them.
Installation
npm install enforce-unique --saveUsage
Simplest usage is just providing a value. If the same value is provided before, enforce method will throw an EnforceUniqueError.
import { EnforceUniqueError, UniqueEnforcer } from 'enforce-unique';
const arrayContainsUniqueItems: number[] = [];
const uniqueEnforcer = new UniqueEnforcer();
const pushUnique = (item: number) => {
try {
arrayContainsUniqueItems.push(
uniqueEnforcer.enforce(item)
)
} catch (error) {
if (error instanceof EnforceUniqueError) {
return 'Item already exists';
}
}
};
pushUnique(1);
// logs 'Item already exists'
console.log(pushUnique(1));Or you can provide a function that returns a value. enforce method will run this function until limits are exceeded
and will return the generated value. If limits are exceeded it will throw an EnforceLimitError.
const uniqueEnforcerEmail = new UniqueEnforcer();
function createRandomUser() {
const firstName = faker.person.firstName();
const lastName = faker.person.lastName();
const email = uniqueEnforcerEmail.enforce(() => {
return faker.internet.email({firstName, lastName});
});
return {
firstName,
lastName,
email,
};
}
// You can be sure that each user in the list has unique email
const users = []
for (let i = 0; i < 100; i++) {
users.push(createRandomUser())
}Default limits
{
maxTime: 50,
maxRetries: 50,
}Options
You can provide options object to change the defaults
const email = uniqueEnforcerEmail.enforce(
() => {
return faker.internet.email({firstName, lastName})
},
{
maxTime: 1000,
maxRetries: 1000,
exclude: [1]
},
);maxTime
The time in milliseconds this method may take before throwing an EnforceLimitError
maxRetries
The total number of attempts to try before throwing an EnforceLimitError
exclude
Exclude specific value(s) from being returned.
Resetting
You can reset the unique enforcer instance to start over, clearing any previously stored values.
const uniqueEnforcer = new UniqueEnforcer();
const value1 = uniqueEnforcer.enforce('value');
uniqueEnforcer.reset();
// There will be no error thrown because of reset.
const value2 = uniqueEnforcer.enforce('value');