Vuejs How to assign an array to another array in such a way that the two arrays are not reactive to changes

Question

I faced with this challenge to assign array to another array such that the arrays won't be reactive on changes from one of the array.

So to achieve this I made a local copy of the same array and assigned one to another but I would love to do stuffs dynamically where I am having the reactive issues.

Below is what am trying to achieve

const ComponentA = {
  data: function() {
    return {
      categories:[
        {
          name: 'Category 1',
          series: [
            {
              name: 'Series 1',
              value: 5
            },
            {
              name: 'Series 2',
              value: 5
            }
          ]
        },
        {
          name: 'Category 2',
          series: [
            {
              name: 'Series 1',
              value: 50
            },
            {
              name: 'Series 2',
              value: 56
            }
          ]
        }
      ],
      tempCategories:[
        {
          name: 'Category 1',
          series: [
            {
              name: 'Series 1',
              value: 5
            },
            {
              name: 'Series 2',
              value: 5
            }
          ]
        },
        {
          name: 'Category 2',
          series: [
            {
              name: 'Series 1',
              value: 50
            },
            {
              name: 'Series 2',
              value: 56
            }
          ]
        }
      ]
    }
  },
  methods: {
    resetCategory() {
      this.tempCategories.forEach((category,i)=>{
        category.series.forEach((series,j)=>{
          this.categories[i].series[j] = series;
        });
      });
    }
  }
}

after computations on categories i can reset the categories array with tempCategories by calling

this.resetCategory() and it works as expected.

Meanwhile I want to be able to do this assignment dynamically whereby when i have copy of the category array I can assign the array to both categories and tempCategories arrays, respectively and after computations with categories array i can reset the categories array with tempCategories array. So I did the following.

initialize(category) {
  this.tempCategories = category;
  this.categories = category;
}

I realize changes in this.categories reflects on this.tempCategories; I've even used the following options

initialize(category) {
  this.tempCategories = category.slice(); 
  //or this.tempCategories = Json.parse(Json.stringify(category));

  this.categories = category.slice();
  //or this.categories = Json.parse(Json.stringify(category));
}

yet the two arrays are still reactive. Please I need help on how to solve this problem.

It seems like your initialize function and this.categories[i].series[j] = series; would still result in the same object existing in both arrays. I typically use _.cloneDeep for stuff like this, though there are other methods. Just make sure you are always creating a deep copy. lodash.com/docs/4.17.15#cloneDeep — chash
– chash, Commented Oct 6, 2019 at 14:56
You could use Array.map or .slice to create an entirely new array. Try replacing the forEach parts with the above. — Varun Agarwal
– Varun Agarwal, Commented Oct 6, 2019 at 14:57
Be careful, map create new array, but the object inside still reference to old obj, so newArray[0].something = newThing will change the oldArray[0] as well. I always use cloneDeep to make sure it is separated. — Sang Dang
– Sang Dang, Commented Oct 6, 2019 at 15:30

amachree tamunoemi · Accepted Answer · 2019-10-06 17:35:19Z

2

Thanks guys, it works now both method

initialize(categories){
  //let copy = _.cloneDeep(categories);
  let copy = JSON.parse(JSON.stringify(categories));
  this.tempCategories = copy;
  this.categories = copy;
},

resetCategories(){
  //this.categories = _.cloneDeep(this.tempCategories);
  this.categories = JSON.parse(JSON.stringify(this.tempCategories)); 
},

answered Oct 6, 2019 at 17:35

amachree tamunoemi

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Diamond · Accepted Answer · 2019-10-06 15:36:28Z

0

There's no such Json. but It may be JSON.

initialize(category) {
  this.tempCategories = JSON.parse(JSON.stringify(category));
  this.categories = JSON.parse(JSON.stringify(category));
}

And you can't prevent fake copy of by

  this.tempCategories = category;
  this.categories = category;

May be those three Arrays are exactly same even one of them is updated.

answered Oct 6, 2019 at 15:36

Diamond

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