如何创建角度指令文本框只允许数字空格和分数

Question

How to create a directive for fraction number so a user can enter the only fraction number just like below.

"10 1/2" // Valid format
"10.25" // Valid format 
"10    1/2" // Invalid format extra spaces found 
"dummy 12 1/2" // Invalid string format found

Answer 1

The following should work..

first create the directive:

@Directive({
  selector: '[exampleDirective]'
})
export class TestDirective {

 constructor() {}

 @HostListener('input', ['$event'])
 ngOnChanges(evt: any) {
  const pattern: RegExp = new RegExp(/^[0-9]+\.?[0-9]*$/);
  if (!pattern.test(evt.target.value)) {
   evt.srcElement.value = evt.srcElement.value.substring(0,evt.srcElement.value.length - 1); // this will erase the last char that does not match the pattern...
  }
 }
}

and then select it in your input

<input exampleDirective/>

Answer 2

You can do something like this.

1) In your html file

<input type="text" (change)="onChange($event.target.value)"/>

2) In your typescript file

onChange(value) {
const reg = /[1-9][0-9]*(?:\/[1-9][0-9])*/; // -> Regex for matching only numbers and fractions
if (!reg.test(value)) { // test() matches string with regex
  // reset textbox here.
}
  }