CODEWITHSUNDEEP
angularvalidation
Nemanja Grabovac
Nemanja Grabovac

Reputation: 878

Validation for blank characters? Angular 4

I need to create some kind of validation on my forms where I don't want user to be able to enter 1++ blank spaces inside fields. So, he can type space but it cannot be only spaces. This is how my validation looks like at the moment:

this.valForm = this.fb.group({
      'firstName': [null, Validators.compose([Validators.required, Validators.maxLength(50)])],
      'lastName': [null, Validators.compose([Validators.required, Validators.maxLength(50)])]
});

I dont know what pattern to use to create this type of validation. Thanks.

Upvotes: 4

Views: 13508

Answers (2)

Patrick Kelleter
Patrick Kelleter

Reputation: 2771

You can just create a custom validator which checks for 

userInputString.trim() !== ''

A validator is not much more than a function which takes a control and returns whether it is valid or not (either as a boolean or a promise/observable).

For more details check out any example out there for custom validators in angular 2+, e.g.

https://blog.thoughtram.io/angular/2016/03/14/custom-validators-in-angular-2.html

Upvotes: 1

user4676340
user4676340

Reputation:

You can do 

'firstName': [null, [Validators.required, Validators.maxLength(50), Validators.pattern(/^((?!\s{2,}).)*$/)]]

If you test it on Scriptular with the chain ^((?!\s{2,}).)*$, you will find that 

Hello darling // Matches
Hello  darling // Doesn't match

This isn't something regexes should do : they're not good at it. A regex is supposed to find an occurence of your expression in a string, not the opposite. But still, they can do it.

If you want to know more, this is called a negative look-around.

Upvotes: 3

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