How to update value for a certain key in a list of objects in Javascript?

Question

I am new to Javascript. I have an object that looks like below

let final_json = {"ab": [{"cd": "ee", "col_val": {}},{"ef": "uu", "col_val": {"gg": "hh"}}]}

Now I want to update the col_val key's value with a defined value of my own. But I also need to ensure that the key cd exists in the given object.

This is what I do

if(final_json["ab"]) {    
    Object.entries(final_json["ab"]).forEach(([key, val]) => {
        if(final_json["ab"][key].hasOwnProperty("cd")) {
            // update the col_val value with {"rr": "ff"}
        }
    })
}

I am just not able to figure out how do I do that. Any help will be appreciated.

holydragon · Accepted Answer · 2019-03-06 09:59:51Z

2

Here I use .forEach and just check for the cd property then update col_val.

let final_json = {"ab": [{"cd": "ee", "col_val": {}},{"ef": "uu", "col_val": {"gg": "hh"}}]}
final_json.ab.forEach(o => {
  if (o.cd) o.col_val = {testKey: "testValue"}
})
console.log(final_json)

answered Mar 6, 2019 at 9:59

holydragon

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Comments

ellipsis · Accepted Answer · 2019-03-06 09:59:02Z

1

Use map and check for cd using hasOwnProperty() function. hasOwnProperty() tells if a specific property is present in the object or not. Refer

let final_json = {
  "ab": [{
    "cd": "ee",
    "col_val": {}
  }, {
    "ef": "uu",
    "col_val": {
      "gg": "hh"
    }
  }]
};
final_json.ab.map(e => {
  if (e.hasOwnProperty('cd'))
      e.col_val = 'my value'
    return e;
})
console.log(final_json)

answered Mar 6, 2019 at 9:59

ellipsis

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1 Comment

Nina Scholz Over a year ago

why map if the returned array is void?

Nina Scholz · Accepted Answer · 2019-03-06 10:01:11Z

0

You could find the wanted object and update the property, if found.

let object = { ab: [{ cd: "ee", col_val: {} }, { ef: "uu", col_val: { gg: "hh" } }] },
    target = (object["ab"] || []).find(o => 'cd' in o);

if (target) {
    target.col_val = { rr: "ff" };
}

console.log(object);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Mar 6, 2019 at 10:01

Nina Scholz

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