angular textarea字数限制，写在ts getter

component.ts

maxlength = 200;

 get textareaLengthHint() {
    const desc = this.validateForm.value.desc
    return `${desc ?.length || 0}/${this.maxlength}`
  }

component.html

    <mat-form-field >
      <mat-label>描述</mat-label>
      <textarea
        matInput
        placeholder="请输入"
        formControlName="desc"
        required
        matTextareaAutosize
        matAutosizeMinRows="6"
        rows="8"
        [maxlength]="maxlength"
      ></textarea>
      <mat-hint align="end">{{ textareaLengthHint }}</mat-hint>
      <mat-error>{{ descError }}</mat-error>
    </mat-form-field>