Incorporating Precision to Decimal Numbers in TypeScript Angular

Having some trouble with this issue and I've tried various solutions without success. This problem is occurring within an Angular project.

The requirement is to always display a percentage number with two decimal places, even if the user inputs a whole number.

Unfortunately, changing the data type is not an option as there is existing code relying on it being a number.

The challenge lies in TypeScript's restriction on using 'var', making it difficult to add extra zeros or round the number to two decimals without them being stripped.

Declaration:

 percent: number;

Some methods I have attempted include:


1:
this.percent = Math.round(this.percent * 1e2) / 1e2;

2:
this.percent = this.percent.toFixed(2); // Error: cannot assign string to number

3:
const percentString = this.percent.toString() + '.00';
this.percent = parseFloat(percentString);

4:
this.percent = Math.round(this.percent * 100) / 100;

5: (Function from another source)

addZeroes(num) {
    let value = Number(num).toString();
    
    const res = num.split('.');
    
    if (res.length === 1 || res[1].length < 3) {
        value = parseFloat(value).toFixed(2);
    }
    
    return value;
}

this.percent = parseFloat(this.addZeroes(this.percent));

6:
this.percent = parseFloat(this.percent).toFixed(2);

7:
this.percent = parseFloat(this.percent.toString()).toFixed(2);

8:
this.percent = Number(this.percent).toFixed(2);

HTML:


<mat-form-field>
    <input
      matInput
      [numbers]="'.'"
      type="text"
      maxlength="5"
      [placeholder]="'Percent'"
      [(ngModel)]="percent"
      (change)="updateDollarAmountNew()"
      numbers
      name="percent">
  </mat-form-field>

Attempts at using pipes in the frontend also encountered issues:


[(ngModel)]="p.percent | number : '1.2-2" // Error: pipe not found

[(ngModel)]="{{percent | number : '1.2-2'}}" // Error: unexpected token 

[(ngModel)]={{percent | number : '1.2-2'}} // Error: Attribute not allowed

[(ngModel)]={{percent | number : 2}} // Error: Expected ':'

// And so forth...

Appreciate any guidance or assistance provided!

Answer №1

All the efforts have been made, yet the missing piece is not being combined. The float parsing is successful and toFixed(2) does generate a string with 2 decimal places. What is required is using them in conjunction:

parseFloat(value).toFixed(2)

Answer №2

Using the number as a numerical value and displaying it in the view is the right approach.

However, there seems to be confusion between binding and formatting. For instance:

[(ngModel)]="{{percent | number : '1.2-2'}}"
could be interpreted (very loosely!) as: bind my model to the string interpolation of...my model.

Consider the following:

<div>{{percent | number : '1.2-2'}}</div>

You can find helpful examples of using the number pipe in the documentation: https://angular.io/api/common/DecimalPipe#example

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