javascript type checking mini library

CheckType.js

/*
Check Type, is used in the beginning of a method.
Here we will check that the Method Parameters is of the correct type.
*/


class Check {
    constructor(obj, errorCode) {
        this.obj = obj;
        this.errorCode = errorCode;
        this.succes = false

        // Guess the object type, as string
        this.objectType = ({}).toString.call(obj).match(/\s([a-zA-Z]+)/)[1].toLowerCase()
    }

    stringOrNull(){
        if (this.objectType === 'string' || this.obj === null)
            this.succes = true
        else{
            this.thowError('stringOrNull()\nVariable is not String or Null, but is: ')
        }
        return this
    }
    string(){
        if ( this.objectType === 'string' && this.obj !== null)
            this.succes = true
        else{
            this.thowError('string()\nVariable is not String, but is: ')
        }
        return this
    }
    
    object(){
        if ( (!!this.obj) && (this.obj.constructor === Object) && this.obj !== null)
            this.succes = true
        else{
            this.thowError('object()\nVariable is not Object, but is: ')
        }
        return this
    }
    
    objectOrNull(){
        if ( (!!this.obj) && (this.obj.constructor === Object) || this.obj === null)
            this.succes = true
        else{
            this.thowError('objectOrNull()\nVariable is not Object or Null, but is: ')
        }
        return this
    }
    
    array(){
        if ( this.objectType === 'array' && this.obj !== null)
            this.succes = true
        else{
            this.thowError('array()\nVariable is not Array, but is: ')
        }
        return this
    }
    
    arrayOrNull(){
        if ( this.objectType === 'array' || this.obj === null)
            this.succes = true
        else{
            this.thowError('arrayOrNull()\nVariable is not Array or Null, but is: ')
        }
        return this
    }
    
    number(){
        if ( this.objectType === 'number' && this.obj !== null)
            this.succes = true
        else{
            this.thowError('array()\nVariable is not Number, but is: ')
        }
        return this
    }
    
    numberOrNull(){
        if ( this.objectType === 'number' || this.obj === null)
            this.succes = true
        else{
            this.thowError('numberOrNull()\nVariable is not Number or Null, but is: ')
        }
        return this
    }
    
    boolean(){
        if ( this.objectType === 'boolean' && this.obj !== null)
            this.succes = true
        else{
            this.thowError('boolean()\nVariable is not Boolean, but is: ')
        }
        return this
    }
    
    booleanOrNull(){
        if ( this.objectType === 'boolean' || this.obj === null)
            this.succes = true
        else{
            this.thowError('booleanOrNull()\nVariable is not Number or Null, but is: ')
        }
        return this
    }  
    
    date(){
        if ( this.objectType === 'date' && this.obj !== null)
            this.succes = true
        else{
            this.thowError('date()\nVariable is not Date, but is: ')
        }
        return this
    }
    
    dateOrNull(){
        if ( this.objectType === 'date' || this.obj === null)
            this.succes = true
        else{
            this.thowError('dateOrNull()\nVariable is not Number or Null, but is: ')
        }
        return this
    }
    
    json(){
        if ( this.objectType === 'json' && this.obj !== null)
            this.succes = true
        else{
            this.thowError('json()\nVariable is not JSON, but is: ')
        }
        return this
    }
    
    jsonOrNull(){
        if ( this.objectType === 'json' || this.obj === null)
            this.succes = true
        else{
            this.thowError('jsonOrNull()\nVariable is not JSON or Null, but is: ')
        }
        return this
    }
    

    thowError(strError){
        let guessObjectType = (Object.prototype.toString.call(this.obj)).toString().split(' ')[1].slice(0, -1);
        let e = new Error();
        let stacktraceAsArray = String(e.stack).split('\n')
        let line = stacktraceAsArray[3].slice(7).replace('(', '').replace(')', '')
        let method = line.split(' ')[0]

        // split to array, and take last element in array
        let filename = line.split('/').pop()
        let filenameShort = filename.split(':')[0]
        let lineNumber = filename.split(':')[1]
        let fileMethodLineNumber = 'Filename: ' + filenameShort + '\nMethod: ' + method + '()' + '\nLine: ' + lineNumber;
        
        let errorString = '\n\n'+ strError + guessObjectType + '\n' +fileMethodLineNumber + '\nErrorCode(optional): ' + this.errorCode +  '\n\nStacktrace:' 
        throw new Error(errorString);
    }
}

/**
 * Type() will check if the Method-Parameter-Variable is of the correct type.
 * 
 * How to use, examples:
 * 
 * type(['a', 'b']).array()
 * type(null).arrayOrNull()
 * type(true).boolean()
 * type(42).number()
 * type({a: 3}).object()
 * type('Hello World').stringOrNull()
 *
 * @param {*} object: any variable
 * @param {number} [errorCode=0] Optional: You can add a errorcode, but is not required.
 * @returns
 */
function type(object, errorCode = 0) {
    let result = new Check(object, errorCode)
    return result;
}

function myMethod(joe){

    // Check: Throw Exeption if wrong type
    type( joe ).array()
    type( joe ).arrayOrNull()
    type( joe ).boolean()
    type( joe ).number()
    type( joe ).object()
    type( joe ).stringOrNull()

    // --------------------------------

    // Method Content...
}



myMethod( ['a', 'b'] )
myMethod( null )
myMethod( true )
myMethod( 42 )
myMethod( {'a': 3} )
myMethod( 'Hello World' )


// TODO: Lav syntaxen om til:
type.int(age, heigth)
type.nullable.int() eller type.null.int() eller type.nullOr.int(age, heigth)
type.check(age > 18, heigth > 120, heigth < 180 )

// Todo: Sikre at metode værdier returner destrictable værdier
function person(){
	return  {name: 'james', age: 33}
}

Let {name, age} = person()

//> name: 'james'
//> age: 33