a simple utility for validating types, such as strings, numbers, arrays, functions and so on
npm install @samislam/checktypesOriginally created in 24 - 01 - 2021
checkTypes is a fast and simple utility for developers to check for types quickly.
You can now finally check for types as quck as possible, no more need for typeof "x" === "string"
- Just a side note before doing anything, I'm using [@samislam/log \[ log() \]](/tmp/.mount_JoplinvV1jiS/resources/app.asar/%5Bfrom%5D%28https:/github.com/samislam/log%29 "%5Bfrom%5D(https://github.com/samislam/log)") which is a very cool utility for logging into the console, it allows for a cool and nice output to the console colored with your favorie color. check it right now on npm, it's free!
checkTypes.isSOMETHING(arg1, arg2, arg3 ...etc)This function is going to check each argument you pass into it, and on the first argument it faces that doesn't match the type that it should, it's going to return false immediatly.
``js`
// functions
log(checkTypes.isFunction(() => {})) // true
log(checkTypes.isAsyncFunction(async () => {})) // true (this one is cool)
log(checkTypes.isAsycOrSyncFunc(() => {})) // true
// Strings
log(checkTypes.isString('Islam')) // true
// Numbers
log(checkTypes.isNumber(100)) // true
// Objects
log(checkTypes.isObject({ name: 'Saleem' })) // true
// Null
log(checkTypes.isNull(null)) // true
// Undefined
log(checkTypes.isUndefined(undefined)) // true
// Symbol
log(checkTypes.isSymbol(Symbol())) // true
// Maps
log(checkTypes.isMap(new Map())) // true
// Dates
log(checkTypes.isDate(new Date())) // true
// Arrays
log(checkTypes.isArray([10, 11])) // true
- All of the methods above have the same syntax and return type (boolean).
Some more examples:
`js`
log( checkTypes.isArray(123456) ) // false
log( checkTypes.isString("yes") ) // true
let x;
log( checkTypes.isUndefined(x) ) // true
log( checkTypes.isUndefined(1, 2, 3, x, 4) ) // false
log( checkTypes.isNumber(1, "2") ) // false
- in up coming versions, there might be more validations, such as isFloatNumber, or maybe I'll be calling it isNumber().isFloat().
- maybe I'll be adding checking for valid string numbers later, such as "123", since "123" is a string but it's a valid number, it contains valid numeric characters.
~ going back to the guide:
*
checkTypes.typeof() provides a united protocol for all of its' return values, all you have to know is to remember that any string that this method is going to return (it's going to return a string by the way) is going to be in a lower case format.
`js`
log(checkTypes.typeOf([])) // array
log(checkTypes.typeOf({})) // object
log(checkTypes.typeOf(1)) // number
log(checkTypes.typeOf(0)) // number
log(checkTypes.typeOf(5)) // number
log(checkTypes.typeOf('hi')) // string
log(checkTypes.typeOf(Symbol())) // symbol
log(checkTypes.typeOf(new Map())) // map
log(checkTypes.typeOf(() => {})) // function
log(checkTypes.typeOf(async () => {})) // asyncfunction
log(checkTypes.typeOf(true)) // boolean
log(checkTypes.typeOf(false)) // boolean
log(checkTypes.typeOf(null)) // null
log(checkTypes.typeOf(undefined)) // undefined
log(checkTypes.typeOf(new Date())) // date
*
`js`
checkTypes.isNumber(throwErr(), "hello").
// # output: Error: "hello" is not a number type, typeof given: string
- remember, it's throwErr and not throwError.
What most of the other modules on github and npm are doing is that they automatically force your code to throw an error because they're hard-coded to do that, that's not how checkTypes works, checkTypes will only throw an error when you want it to throw an error.
To describe how checkTypes.throwErr() works behind the scenes, calling checkTypes.throwErr() is going to return an object, if you tried to log() it to the console, you'll see it's an object that holds a Symbol (btw: Symbol is an ES6 JS Type):
`js`
log( checkTypes.throwErr() )
// # output: { _identifier: Symbol() }
You don't want to miss with this, this is just a private implementation that checkTypes is going to see so it can understand that it should throw an error at that particular mis-match or not.checkTypes
This object folks that you can see in the output is a unique object that is used to communicate with , it tells it to do things.
The key thing that allows checkTypes.isSOMETHING() to know that the given argument checkTypes.throwErr is not something to check the typeof is the _identifier thing.
All you have to know here is that whenever you want the checkTypes.isSOMETHING() method to throw an error once validation is failed, you'll pass the checkTypes.throwErr() as one of the arguments in your checkTypes.isSOMETHING() function (at the position you want it to throw an error). for example:
`js`
checkTypes.isString(checkTypes.throwErr(), 123)
// # output: Error: 123 is not a string type, typeof given: number
// ... the stack of the error here
"at the position you want it to throw an error" means you can write checkTypes.throwErr() anywhere in between the function arguments, as the first, second, third or any argument position you want, you're not required to write checkTypes.throwError() as the first argument in checkTypes.isSOMETHING(), but.. here is the difference:
checkTypes will only throw an error for checkTypes.throwErr() at the time you want it to throw an error, so if you passed checkTypes.throwErr() as the second argument in checkTypes.isSOMETHING(), then only for the rest of the arguments after the position where checkTypes.throwErr() is registered within the argument list checkTypes.throwErr() is going to throw an error, while for all of the arguments before the position where throwErr is registered, checkTypes is not going to see that you want to throw an error, so no error is thrown for these.
For example:
`js`
checkTypes.isNull(123, checkTypes.throwErr(error), "incorrect one")
// returns false for the 123 but doesn't throw an error, that's because it has already returned
another example:
`js`
checkTypes.isNull(null, checkTypes.throwErr(error), 123)
// throws an error because of 123
- if you understand this part, then you already understand by now how checkTypes.isSOMETHING() is going to treat the checkTypes.generateErr() too (checkTypes.generateErr() will be mentioned later down).checkTypes.throwErr()
- if was the last argument within the list, checkTypes is Not going to throw any error because of what described above.checkType.isUndefined(checkTypes.throwErr())
- if you used then everything is going to work as you expect, no error will be thrown, since the "nothing given" in JavaScript is called "undefined".checkTypes.isUndefined()
- extra example , this is going to return true.
checkTypes.throwError([obj]) takes a one optional argument, this argument must be an object.
The object you pass here will be used to display an error message, therefore, inside this object you can write anything you want, but remember, there are certain special properties that are already built into the JavaScript Error instances (btw: the error shown to the user is an object that inherits from The JavaScript Error class). therefore you can for example modify the message property to show a custom message to the user, you may also change the stack as an example, but you're not limited to only these, you can add your own properties to that object, and they'll be on the user's screen.
- most of the things you read here are the same concipts and logic behind checkTypes.generateErr() which you'll read about down in just few seconds.
For example:
`js`
const error = { message: "that's not valid" }
checkTypes.isNull(checkTypes.throwErr(error), 'hi')
// Error: that's not valid
// ... the stack of the error
another example:
`js`
const userInput = "water";
const error = { message: "wow, you was about to make a mistake!"}
checkTypes.isUndefined(checkTypes.throwErr(error), userInput)
// do other things ...
// nothing will happen, because validation succeed
Don't stop reading here, if you're deciding to stop reading from here, take a look at the special interpretted characters inside the message property that you'll provide ["{!}", "{$}", "{#}"], they're mentioned down.
*
checkTypes.generateError will receive an object from you, and will inject a property called _identifier inside of it, and then return your object.
- everything here is the same as checkTypes.throwErr(), so you should read it first, then come back to here to read more.
The only difference between generateErr() and throwErr() in how they're treated by checkTypes.isSOMETHING() is the following:
- throwErr(), checkType.isSOMETHING() is going to throw the error.generateErr()
- , is going to return the error object so you can save it in a variable and do some other stuff with it.
For Example:
`js`
const userInput = []
const theError = checkTypes.generateErr({ message: "the given argument is not an array!"})
const state = checkTypes.isArray(theError, userInput)
log(state) // true
- if the validation succeed, the returned value will be true.
- if the validation failed, the returned value will be an object that holds all your properties of the object you gave to checkTypes.generateErr(). this object inherits from the JavaScript Error class.
another example:
`js`
const userInput = "mera naam islam hai, BTW: I'm not Indian :D"
const theError = checkTypes.generateErr({ message: "the given argument is not an array!"})
const state = checkTypes.isArray(theError, userInput)
log(state)
// Error: then given argument is not an array!
// ...the stack of the error
log("As you can see, the error is not thrown, the code will continue..")
// As you can see, the error is not thrown, the code will continue..
*
as I mentioned above in the throwErr and the generateErr sections, is that you can write an optional message to diplay for the user, checkTypes provides three special strings that are interpritted by checkTypes to human readable strings.
| Special character | Description |
| --- | --- |
| {#} | translated to the pre-defined template, for example, by default, if a the user input was 1234, and the required type is an array, the {#} is going to be translated to "1234" is not an array, typeof given: string".
\- you can configure the default template, see the next section for how. |
| {!} | translated to the given type by the user, for example, if the user entered , the {!} is going to be number |1234
| {$} | translated to the given user input, for example, if the user entered , the {$} is going to be translated to 1234 |
Examples:
`js`
const userInput = "مرحباً بك"
const error = checkTypes.generateErr( { message: "{$} is not allowed, the only allowed type is an array, the type you gave me is {!}"} )
const status = checkTypes.isArray(error, userInput)
if(status != true) log.error(status.message)
// "مرحباً بك" is not allowed, the only allowed type is an array, the type you gave me is string
another example:
`js`
const userInput = "bilgisayarım yavaş"
const error = checkTypes.throwErr( { message: "{$} is not allowed, the only allowed type is an array, the type you gave me is {!}"} )
checkTypes.isArray(error, userInput)
// Error: "bilgisayarım yavaş" is not allowed, the only allowed type is an array, the type you gave me is string
// the stack of the error ...
- these special symbols are treated as mentioned above in both throwErr() and generateErr().
*
, You can change the default template used for the error messages.
all configurations you apply will also apply to any other file you import checkTypes to, thanks to its' singleton design.This means that you can change the template from file A, and use that template from module B, C and D without reconfiguring
checkTypes on each new import.The
checkTypes.config objectas for the current version, the only configurations you can make to checkTypes is to change how the default templates looks like.
checkTypes.config is not a function, it's an object that holds properties, for this version, there is only one thing to configure which is the errorMessages object.`js
log.s(checkTypes.config)
// you can use console.log
/*
{
errorMessages: {
function: '{$} is not a function, typeof given: {!}',
asyncfunction: '{$} is not an async function, typeof given: {!}',
string: '{$} is not a string, typeof given: {!}',
number: '{$} is not a number, typeof given: {!}',
object: '{$} is not an object, typeof given: {!}',
null: '{$} is not a null type, typeof given: {!}',
undefined: '{$} is not an undefined, typeof given: {!}',
symbol: '{$} is not a symbol, typeof given: {!}',
map: '{$} is not a map type, typeof given: {!}',
date: '{$} is not a date, typeof given: {!}',
array: '{$} is not an array, typeof given: {!}',
AsyncOrSyncFunction: '{$} is not an Async nor Sync Function , typeof given: {!}',
defaultTemplate: '{$} is not a valid type , typeof given: {!}'
}
}
*/
`
you can modify these defaults by writing your own:
js
checkTypes.config.errorMessages.function = "Ihre Eingabe "{$}" ist keine Funktion!"
`
- you can use the special interpretted characters the same way you can use them on and generateErr({message}). [{!}, {$}, {#}].
- configuring this object will configure all your other modules that depends on checkTypes, so no need to call checkTypes.config multiple times.
FAQ
Q: It seems like checkTypes is unable to memorize my default customized configurations from one module to another?
A: Please make sure that your module that have the configurations defined inside of it is being loaded an invoked by your code before the the other modules, this is very logical, you have to set checkTypes.config.errorMessages.string = "some template" first, and then you can use your custom template checkTypes.generateErr(message)` afterwards.