Type checker

This code does type checking in typescript or javascript. This was created so you easily can add type checking to your code, especially if when getting user input as requests and the if statements is getting long.

Methods

The methods that exists in the Checker class are:

checkVariableType

This method checks if the variable is of the correct type. The parameters are:

• variable: The variable that you want to check the type of.
• type: The type that you want to check the variable against.
• error: [optional] The error that you want to throw if the variable is not of the correct type.

checkNumber

This method checks if the variable is a number and if it is it checks against requirements passed in. The parameters are:

• variable: The variable that you want to check the type of.
• error: [optional] The error that you want to throw if the variable is not of the correct type. Pass in undefined if you don't want to throw an error.
• requirements: [optional] The requirements that you want to check the variable against. Has to be of type NumberRequirements.
• radix: [optional] The radix that you want the number to be. Default is 10.

checkFloat

This method checks if the variable is a float and if it is it checks against requirements passed in. The parameters are:

• variable: The variable that you want to check the type of.
• error: [optional] The error that you want to throw if the variable is not of the correct type. Pass in undefined if you don't want to throw an error.
• requirements: [optional] The requirements that you want to check the variable against. Has to be of type NumberRequirements.

Types

The types which currently can be checked are:

string
number
boolean
object
array
function
undefined
null
regexp
Date
Error

NumberRequirements

The number requirements are:

NumberRequirements {
    min: number [optional]
    max: number [optional]
    equalTo: number[] [optional]
    notEqualTo: number[] [optional]
}

How to get started

Run npm i type-checker-ts At the top of the file import with the following command:

import { Checker, Types } from 'type-checker-ts';

To run the code you can use the following example:

const checker = new Checker();

checker.checkVariableType('hello world', Types.STRING); // returns true

checker.checkVariableType('hello world', Types.STRING, new Error('Is not a string')); // returns true

checker.checkVariableType(2, Types.STRING, new Error('Is not a string')); // throws error

checker.checkVariableType(2, Types.STRING); // return false

try {
    checker.checkVariableType(2, Types.STRING, new Error('Is not a string'));
} catch (e: any) {
    if (e.message === 'Is not a string') {
        // will get here since 2 is not a string
    } else {
        throw e;
    }
}