https://www.zhihu.com/question/23529765（方法來源）

html

<input style="display:none" type="text" class="login-password" [(ngModel)]="passwordValue" formControlName="passwordTwo">
<input nz-input type="text" formControlName="password"  class="log-password" placeholder="請輸入密碼" [(ngModel)]="passwordVal" (ngModelChange)="chagePassword()">

ts

    passwordVal = '';
    passwordValue = '';
    trueValue = [];//儲存真實資料的陣列
    beforeLength = 0;//隱藏框value的長度
    chagePassword() {
        let nowLength = this.passwordVal.length;// 變化後的長度
        if (nowLength > this.beforeLength) {//長度增加時
            this.trueValue.push(this.passwordVal[nowLength - 1]);
            
 
++this.beforeLength;
        } else {//長度減少時
            this.trueValue.pop();
            --this.beforeLength;
        }
        this.passwordValue = this.trueValue.join('');
        let nowValue = '';//轉換為圓點
        for(let i = 0; i < nowLength; ++i){
            nowValue += '•';
        }
        
 
if(nowValue){
            this.eleRef.nativeElement.querySelector('.log-password').value = nowValue;
        }
    }