Object of array of objects. Get the length of all values with the same property

user_8767435 0
Viewed 1279

I have an object that looks like this: 

    var obj = {
      "array1": [
        {
          "label": "something1",
          "ref": "option2a"
        },
        {
          "label": "something2",
          "ref": "option2b"
        },
        {
          "label": "something3",
          "ref": "option2a"
        },
        {
          "label": "something4",
          "ref": "option2a"
        },
        {
          "label": "something5",
          "ref": "option2a"
        }
      ],
      "array2": [
        {
          "label": "something6 is the longest label",
          "ref": "option3a"
        },
        {
          "label": "Other",
          "ref": "option3b"
        }
      ]
    }

I want to get the length of the longest label. In this case I would want to return 17. Because the longest label is "somethinglongest" which has a length of 17.

max object for-loop arrays javascript
6 Answers
  • Use .concat() and Object.values() to get a single array having all objects.
  • Use .map() to an array containing length of strings.
  • And finally use .reduce() to get the length of longest string.

let data = {
    "array1": [
        {"label": "something1", "ref": "option2a"},
        {"label": "something2", "ref": "option2b"},
        {"label": "something3", "ref": "option2a"},
        {"label": "something4", "ref": "option2a"},
        {"label": "something5", "ref": "option2a"}
    ],
    "array2": [
        {"label": "somethinglongest", "ref": "option3a"},
        {"label": "Other", "ref": "option3b"}
    ]
};

let reducer = arr => [].concat(...Object.values(arr))
                       .map(({ label }) => label.length)
                       .reduce((r, c) => r > c ? r : c);

console.log(reducer(data));

user_59336560

Get an array of all the objects inside the sub arrays.

Calculate the max length of the values mapping each value to its length:

var obj = {
  "array1": [{
      "label": "something1",
      "ref": "option2a"
    },
    {
      "label": "something2",
      "ref": "option2b"
    },
    {
      "label": "something3",
      "ref": "option2a"
    },
    {
      "label": "something4",
      "ref": "option2a"
    },
    {
      "label": "something5",
      "ref": "option2a"
    }
  ],
  "array2": [{
      "label": "somethinglongest",
      "ref": "option3a"
    },
    {
      "label": "Other",
      "ref": "option3b"
    }
  ]
};

console.log(Math.max(...Object.values(obj).flat().map(o => o.label.length)));

user_26527590

A straight-forward approach:

let obj = {
      "array1": [
        {"label": "something1", "ref": "option2a"},
        {"label": "something2", "ref": "option2b"},
        {"label": "something3", "ref": "option2a"},
        {"label": "something4", "ref": "option2a"},
        {"label": "something5", "ref": "option2a"}
      ],
      "array2": [
        {"label": "something6 is the longest label", "ref": "option3a"},
        {"label": "Other", "ref": "option3b"}
      ]
};

let longest = 0
for (key in obj){
    if (!obj.hasOwnProperty(key)) continue;
    for (let x of obj[key]){
        if (x.label.length > longest)
            longest = x.label.length;
    }
}
console.log(longest);

user_74343650

Another option is to iterate through the own properties of the obj object and check if the length of each label is longer than the previous longest length.

var obj = {
  "array1": [
    { "label": "something1", "ref": "option2a" },
    { "label": "something2", "ref": "option2b" },
    { "label": "something3", "ref": "option2a" },
    { "label": "something4", "ref": "option2a" },
    { "label": "something5", "ref": "option2a" }
  ], "array2": [ 
    { "label": "somethinglongest", "ref": "option3a" },
    { "label": "Other", "ref": "option3b" }
  ]
}

let longest = 0;

for (key in obj) {
  if(obj.hasOwnProperty(key)) {
    obj[key].forEach(item => {
      if (item.label.length > longest) longest = item.label.length;
    })
  }
}

console.log(longest);

user_65257240

You could look for objects and then for the wanted key. This works for an arbitrary depth of data.

function getLongest(object, key) {
    return Object.values(object).reduce((l, v) => {
        if (key in v) return Math.max(l, v[key].length);
        if (v && typeof v === 'object') return Math.max(l, getLongest(v, key));
        return l;    
    }, 0);
}

var data = { array1: [{ label: "something1", ref: "option2a" }, { label: "something2", ref: "option2b" }, { label: "something3", ref: "option2a" }, { label: "something4", ref: "option2a" }, { label: "something5", ref: "option2a" }], array2: [{ label: "somethinglongest", ref: "option3a" }, { label: "Other", ref: "option3b" }] };

console.log(getLongest(data, 'label'));

user_14476750

You can use this 1 line statement.

let maxLen = Math.max(...Object.keys(obj).map((key) => Math.max(...obj[key].map((o) => o.label.length))));

Example on Node REPL

> var obj = {
...       "array1": [
...         {
.....           "label": "something1",
.....           "ref": "option2a"
.....         },
...         {
.....           "label": "something2",
.....           "ref": "option2b"
.....         },
...         {
.....           "label": "something3",
.....           "ref": "option2a"
.....         },
...         {
.....           "label": "something4",
.....           "ref": "option2a"
.....         },
...         {
.....           "label": "something5",
.....           "ref": "option2a"
.....         }
...       ],
...       "array2": [
...         {
.....           "label": "somethinglongest",
.....           "ref": "option3a"
.....         },
...         {
.....           "label": "Other",
.....           "ref": "option3b"
.....         }
...       ]
...     }
undefined
>
> Math.max(...Object.keys(obj).map((key) => Math.max(...obj[key].map((o) => o.label.length))))
16
>

Detailed overview

let keys = Object.keys(obj);

let maxLens = keys.map((key) => {
    let arr = obj[key];
    return Math.max(...arr.map((o) => o.label.length))
});

let max = Math.max(...maxLens);

console.log(keys);    // [ 'array1', 'array2' ]
console.log(maxLens); // [ 10, 16 ]
console.log(max);     // 16

And here is the example to help you.

> Math.max(4, 5, 7)
7
>
> Math.max([4, 5, 7])
NaN
>
> Math.max(...[6, 7])
7
>
> let a = [2, 4, 5]
undefined
>
> a2 = a.map((num) => num ** 2)
[ 4, 16, 25 ]
>
> a3 = a.map((num) => num + 2)
[ 4, 6, 7 ]
>
user_66151630
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