为什么更改一个属性（对象）也会在另一个单独声明的属性中发生变化？

Question

我有2个这样声明的属性：

ngOnInit() {

this.defaultRequirements = myData.property1.countryDocument; //should never change

this.filteredRequirements = myData.property1.countryDocument; 

}

当我运行此onFilter函数时，defaultRequirements属性也会发生突变。

onFilter(selectedSections) {

    let index = -1;

    this.defaultRequirements.forEach(country => {

      index++;

      const filteredSectionsList = [];

      country.section.forEach(section => {

        selectedSections.value.forEach(selectedSelection => {

          const selection = selectedSelection.split(/\s*[-]\s*/);  

          if (country.countryCode === selection[0]) {

            console.log('matched');

            filteredSectionsList.push(section);

          }

        });

        const countryObj = Object.assign({}, country, {

          section: [...filteredSectionsList]

        })

// Here is the issue, when filtering, this.defaultRequirements also gets changed!

        this.filteredRequirements[index] = countryObj;

      })

    })

}

问题

我不明白如何对this.filteredRequirements进行突变也对this.defaultRequirements进行突变（它们都等同于同一件事）！如何避免这种行为并使defaultRequirements不受filteredRequirements上所做更改的影响？

Answer 1

试试这个：ngOnInit() {    this.defaultRequirements = JSON.parse(JSON.stringify(myData.property1.countryDocument));       this.filteredRequirements = JSON.parse(JSON.stringify(myData.property1.countryDocument));}或者ngOnInit() {    this.defaultRequirements = {...myData.property1.countryDocument}    this.filteredRequirements = {...myData.property1.countryDocument}}