Count number of all specific keys (or values) in json object/array- JavaScript/Angular?-CodePudding

I have large nested json object like this, and I want to count the number of pets in the whole object. How can achieve that? I've tired Object.keys(obj[0]).length but not successful of the desired result. Also how can I go deeper into array for counting for example some nested value like color in pet?

What is the good tutorial for working with multi level arrays in JavaScript or Angular?

obj = [
 {
        "person": {
          "name": "a",
        },
        "pet": {
          "name": "1"
        }
      },

      {
        "person": {
          "name": "b",
        },
        "pet": {
          "name": "2",
          "color": "black",
          }
        },

      {
        "person": {
          "name": "c",
        },
        "pet": {
          "name": "3",
          "color": "red",
          }
        }
]

CodePudding user response：

Filter the array with pet property and pet's color property and perform array count.

let obj = [
    {
        "person": {
            "name": "a",
        },
        "pet": {
            "name": "1"
        }
    },

    {
        "person": {
            "name": "b",
        },
        "pet": {
            "name": "2",
            "color": "black",
        }
    },

    {
        "person": {
            "name": "c",
        },
        "pet": {
            "name": "3",
            "color": "red",
        }
    }
];
let petItemCount = obj.filter(x => x["pet"]).length;
console.log(petItemCount);

let petItemWithColorCount = obj.filter(x => x["pet"] && x["pet"]["color"]).length;
console.log(petItemWithColorCount);

CodePudding user response：

let pets = 0;
obj.map( item => {
  if(item.pet) {
    pets  = 1;
  }
})

CodePudding user response：

Sounds like reducing would be a fit:

numberOfPetColors = obj.reduce(
 (sum, { pet }) => pet.color !== undefined ?   sum : sum, 
0)); // -> starting count value

If using lodash you can also use sumBy:

_.sumBy(obj, (arrayEntry) => arrayEntry.pet.color)