Only numerical values are permitted, and numbers may not commence with 0 in Angular 4

Hey there, I'm new to Angular 4 and in need of help validating a form field. I want to allow only numbers, but the first digit should not be 0.

I've tried different solutions that I found, but none of them worked for me.

Could someone please assist me with this?

This is what I have in my app.component.ts file:

NumberOnly(event: any) {
    const pattern = /^([1-9][0-9]*|0)$/;
    let inputChar = String.fromCharCode(event.charCode);
    if (!pattern.test(inputChar)) {
      event.preventDefault();

    }
  }

The code above allows only numbers, however, it does not validate the rule against having the first digit as ZERO.

Answer №1

Experiment with Regular Expressions: /^(?:(?:[1-9][0-9]*)|0)$/

See it in action

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