Looping through array of objects and change a value of a key in JavaScript

Question

I have the following json array which i have destructured from a service response in my angular application.

this.selectedList = [
  [
    {
      "meterNumber": "Z00001410",
      "utilType": "elec",
      "mprnGprn": "3100000334",
      "isChecked": true
    },
    {
      "meterNumber": "Z00001410",
      "utilType": "gas",
      "mprnGprn": "1000003344",
      "isChecked": true
    }
  ],
  [
    {
      "meterNumber": "Z00001410",
      "utilType": "elec",
      "mprnGprn": "1000003344",
      "isChecked": true
    }
  ],
  [
    {
      "meterNumber": "Z00001410",
      "utilType": "elec",
      "mprnGprn": "1000003344",
      "isChecked": true
    }
  ]
]

What i need to do is to iterate through the list and change the isChecked value to false on a click event. I have tried the following

  selectAll(){
    this.selectedList = this.data.reportList.map((meter) => meter.pm);
    this.newList = this.selectedList.map((data) => {
      data.forEach(item => item.isChecked = false);
  });
  console.log(this.newList);
  }

the above code is changing the value to false, but when i try to console the newList, its an array of undefined values. Is it the best way to do this or what am i doing wrong here.

Thanks in Advance.

technical nit, but very important, especially for someone with 1000+ rep: JSON is string data. Nothing else. If you're talking about actual data structures, that has nothing to do with JSON. That's just JS objects. And based on your code, you're showing a regular JS array. Why does your post title have "json"? The code you're showing is normal JS, not JSON. — Mike 'Pomax' Kamermans
– Mike 'Pomax' Kamermans, Commented Nov 12, 2020 at 0:08

Daniel Beck · Accepted Answer · 2020-11-12 00:16:29Z

4

You just need to add return data from each iteration of your map:

this.selectedList = [
  [{
      "meterNumber": "Z00001410",
      "utilType": "elec",
      "mprnGprn": "3100000334",
      "isChecked": true
    },
    {
      "meterNumber": "Z00001410",
      "utilType": "gas",
      "mprnGprn": "1000003344",
      "isChecked": true
    }
  ],
  [{
    "meterNumber": "Z00001410",
    "utilType": "elec",
    "mprnGprn": "1000003344",
    "isChecked": true
  }],
  [{
    "meterNumber": "Z00001410",
    "utilType": "elec",
    "mprnGprn": "1000003344",
    "isChecked": true
  }]
]

selectAll = () => {
  this.newList = this.selectedList.map((data) => {
    data.forEach(item => {item.isChecked = false});
    return data;
  });
  console.log(this.newList);
}

selectAll()

edited Nov 12, 2020 at 0:16

answered Nov 12, 2020 at 0:10

Daniel Beck

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Comments

HenryDev · Accepted Answer · 2020-11-12 00:18:21Z

Keep in mind that you need to return a value when using map. Here's a working solution:

this.selectedList = [
  [
    {
      "meterNumber": "Z00001410",
      "utilType": "elec",
      "mprnGprn": "3100000334",
      "isChecked": true
    },
    {
      "meterNumber": "Z00001410",
      "utilType": "gas",
      "mprnGprn": "1000003344",
      "isChecked": true
    }
  ],
  [
    {
      "meterNumber": "Z00001410",
      "utilType": "elec",
      "mprnGprn": "1000003344",
      "isChecked": true
    }
  ],
  [
    {
      "meterNumber": "Z00001410",
      "utilType": "elec",
      "mprnGprn": "1000003344",
      "isChecked": true
    }
  ]
]

selectAll = () => {
    this.selectedList = this.selectedList.map(subArray => {
        subArray.forEach(_ => _.isChecked = false);
        return subArray;
    });
    console.log(this.selectedList)
}

selectAll();

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