How to add objects inside array javascript

Question

This is my array:

array = [
 { animal: 'dog', leg: 4, age: 3 },
 { animal: 'chicken', leg: 2, age: 2 },
 { animal: 'egg'},
];

This is my desired array:

desiredArray = [
 { animal: 'dog', leg: 4, age: 3, sum: 7 },
 { animal: 'chicken', leg: 2, age: 2, sum: 4 },
 { animal: 'egg', sum: 0 },
];

I want to add a property to each object in the array which is the sum of the leg and the age. If leg or age is null, it will have a value of 0.

Answer 1

you can use Array.map function and do the validation directly like this in plain javascript itself

const array = [
 { animal: 'dog', leg: 4, age: 3 },
 { animal: 'chicken', leg: 2, age: 2 },
 { animal: 'egg'},
];
const output = array.map(val => ({...val, sum: (val.leg || 0) + (val.age || 0)}));
console.log(output);

Answer 2

you can use javascript each loop

var array = [
 { animal: 'dog', leg: 4, age: 3 },
 { animal: 'chicken', leg: 2, age: 2 },
 { animal: 'egg'},
 ];
 $.each(array,function(k,v){
 var total=0;
 if(v.leg)
 total=v.leg;
 if(v.age)
 total=total+v.age 
 v.sum=total
 });
 console.log(array);

Answer 3

array = [
 { animal: 'dog', leg: 4, age: 3 },
 { animal: 'chicken', leg: 2, age: 2 },
 { animal: 'egg'},
];
resultArray = []
for(var item of array) {
 item['sum'] = ('leg' in item?item.leg:0) + ('age' in item?item.age:0)
 resultArray.push(item)
}
console.log(resultArray)

Answer 4

Please Try with one it will work for you and do let me know. I am here looping the array of objects using array.map then adding a new property to the object with the resultant value.

The Object.assign() method is used to copy the values of all enumerable own properties from one or more source objects to a target object. It will return the target object.

const result = array.map((el) => {
 const o: any = Object.assign({}, el);
 o.sum = (el.leg || 0) + (el.age || 0)
 return o;
})

• LeoGarcia: I am using angular and it says property sum does not exist on type
• sibabrat swain: Opps that is due to tslint. Just change const o: any = Object.assign({}, el);. It will work. Check the edited solution, please. I have tested it in angular8 platform.
• LeoGarcia: this returns sum of 0. Expected is 9. { animal: 'egg', leg: 9},
• sibabrat swain: I have updated the answer. It will work in all the conditions.

Answer 5

const array = [
 { animal: 'dog', leg: 4, age: 3 },
 { animal: 'chicken', leg: 2, age: 2 },
 { animal: 'egg'},
 { animal: 'special animal', leg: 5},
];
const getDesiredArray = (array) => {
 const desiredArray = array.map( animal => {
 if(animal.leg || animal.age) {
 animal.sum = animal.leg || 0 + animal.age || 0;
 } else {
 animal.sum = 0;
 }
 return animal;
 })
 return desiredArray;
}
console.log(getDesiredArray(array));

Answer 6

If you you have multiple data then you can destructure it and make use of reduce method. Here is a working example:

var array = [ { animal: 'dog', leg: 4, age: 3 }, { animal: 'chicken', leg: 2, age: 2 }, { animal: 'egg'}];
var result = array.map(({animal, ...rest})=>({animal,...rest, sum:Object.values(rest).reduce((s,v)=>s+v,0)}));
console.log(result);

Answer 7

Because you used objects in this code , I think the best approach for this code is JavaScript Object Oriented approach. using this approach your objects will have sum property itself. When you need to see the sum value all you have to do is call it.

I think you in a middle of learning javascript so I post both ES5 and ES6 codes here.

//ES5 solution
var Animal = function (animalName, leg = null, age = null, sum = null) {
 this.animalName = animalName;
 this.leg = leg;
 this.age = age;
 this.sum = sum; //you can set this as this.sum = null if you dont want to assign value when define.
};
Animal.prototype.calcSum = function () {
 if (this.age === null || this.leg === null) { // I used null value , because you mentioned it. In javascript undefined variable value is undefined not null. if you mean 0 or undefined? you can change it.
 this.sum = 0;
 
 } else {
 this.sum = this.leg + this.age;
 }
};
var dog = new Animal("dog", 4, 3);
var chicken = new Animal("chicken", 2, 2);
var egg = new Animal("egg");
var array = [dog, chicken, egg];
array[0].calcSum(); //this will update the value of sum in dog object
array[1].calcSum(); //this will update the value of sum in chicken object
array[2].calcSum(); //this will update the value of sum in egg object
//ES6 solution
class Animal {
 constructor(animalName, leg = null, age = null, sum = null) {
 this.animalName = animalName;
 this.leg = leg;
 this.age = age;
 this.sum = sum;
 }
 calcSum() {
 if (this.age === null || this.leg === null) { // I used null value , because you mentioned it. In javascript undefined variable value is undefined not null. if you mean 0 or undefined? you can change it.
 
 this.sum = 0;
 
 } else {
 this.sum = this.leg + this.age;
 }
 };
}
const dog = new Animal("dog", 4, 3);
const chicken = new Animal("chicken", 2, 2);
const egg = new Animal("egg");
let array = [dog, chicken, egg];
array[0].calcSum(); //this will update the value of sum in dog object
array[1].calcSum(); //this will update the value of sum in chicken object
array[2].calcSum(); //this will update the value of sum in egg object

you can get the sum value using below code line.

console.log(array[1].sum);