動態參數 startWith Rxjs

Question

我希望在值更改時添加多個輸入字段的發射值。

問題是：有多個字段，我希望它是動態的，因為我不知道我可以提前擁有多少個字段！

// In this case i have 3 input fields 
var keyObjectFields = ["0", "1", "2"];


const observedValues = keyObjectFields.map(key => this.credentialsForm.controls[key].valueChanges
    .map(value => +value).startWith(0, 0, 0))

const resSurface = combineLatest(observedValues)
    .pipe(map(([value0, value1, value2]) => { return value0 + value1 + value2 }));

resSurface.subscribe(val => { this.surface = val });

Answer 1

使用startWith(0)開始觀察到的每個具有0。使用array.reduce來計算陣列的總和。

// In this case i have 3 input fields 
var keyObjectFields = ["0", "1", "2"];


const observedValues = keyObjectFields.map(
  key => this.credentialsForm.controls[key].valueChanges.pipe(
    map(value => +value),
    startWith(0)
  )
);

const resSurface = combineLatest(observedValues).pipe(
  map(values => values.reduce((sum, curr) => sum + curr))
);

resSurface.subscribe(val => { this.surface = val });