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Accepted
hubman
Asked: 2020-07-24 07:43:18 +0800 CST 2020-07-24 07:43:18 +0800 CST

Iterate multilevel object

  • 772

I have a 3 level object with a code that iterates for each level, if in case the levels increase I would like to improve it so that it is more dynamic, can recursion be used, or even non-recursion but how could it be optimized?

var obj = [{
  "seccion1": {
    "level1": {
      first: "John",
      last: "Doe"
    },
    "level2": {
      first: "juan",
      last: "perez"
    }
  }
}]


obj.forEach(function(item) {

  Object.keys(item).forEach(function(key) {
    let value = item[key];
    
    Object.keys(value).forEach(function(key2) {
       console.log(value[key2].first, value[key2].last);
     
    });
  });
});

The result should be:seccion1 level1 john doe level2 juan perez

javascript

4 Answers

  1. Best Answer

    You must make a recursive function, you avoid repeating code:

    var obj = [{
  "seccion1": {
    "level1": {
      first: "John",
      last: "Doe"
    },
    "level2": {
      first: "juan",
      last: "perez"
    }
  }
}]

function iterarObjeto(objeto){
  Object.keys(objeto).forEach(function(key) {
  
    if(typeof(objeto[key]) === "object"){
     console.info(`objeto ${key} vamos a iterar!`);
     iterarObjeto(objeto[key])
    }else{
      console.log(objeto[key])
    }

  });
}
obj.forEach(function(item) {
  iterarObjeto(item)

});

    We can avoid the last iteration, but you need to know the last iteration, you avoid traversing the object again, the example below:

    const obj = [{
  "seccion1": {
    "level1": { first: "John", last: "Doe"  } ,
    "level2": { first: "juan", last: "perez"}
  }
}]
const ultimaIteracion = 2

function iterarObjeto(objeto, numeroIteracion){
  if (numeroIteracion == ultimaIteracion){
    console.log(objeto);
    return;
  }
  Object.keys(objeto).forEach(function(key) {
  
    if(typeof(objeto[key]) === "object"){
     console.info(`objeto ${key} vamos a iterar!`);
     iterarObjeto(objeto[key], numeroIteracion + 1)
    }

  });
}
obj.forEach(function(item) {
  iterarObjeto(item, 0)

});

    • 8

  2. Using the divide and conquer strategy : An object of this type can have as properties a primitive type (string, number, bigint, null, undefined...) or another nested object.

    let obj = {
  a : 'primitivo',
  b : 0,
  c : null,
  d : {}, //objeto vacío
  e: [] //objeto array
};


function tipos(o) {
  for (let key in o) {
    console.log('La propiedad ', key,' es ',typeof o[key]);
  }
}

tipos(obj);

    So you have a base case: the property is a primitive. The recursive case is when the property of the object is another object:

    var obj = [{
  "seccion1": {
    "level1": {
      first: "John",
      last: "Doe"
    },
    "level2": {
      first: "juan",
      last: "perez"
    }
  }
}]

function printObject(o) {
  let text = '';
  Object.keys(o).forEach(key => {
    if (typeof o[key] === 'object') {
      // objeto: mostramos la clave y hacemos una llamada recursiva
      text += `${key} ${printObject(o[key])}`; 
    } else {
      text += `${o[key]} `; //primitivo: directamente imprimimos el valor
    }
  });
  return text;
}

console.log(printObject(obj));

    • 7

  3. Limiting Pablo Lozano's answer, a couple of lines of code can be reduced by changing the ifby conditional ?and :initializing the variable textwhen declaring the function, being as follows:

    var obj = [{
  "seccion1": {
    "level1": {
      first: "John",
      last: "Doe"
    },
    "level2": {
      first: "juan",
      last: "perez"
    }
  }
}]

function printObject(o,text = '') {
  Object.keys(o).forEach(key => {
    typeof o[key] === 'object' ? text += `${key} ${printObject(o[key])}` : text += `${o[key]} ` 
  });
  return text;
}

console.log(printObject(obj));

    And this would be the most optimal way to iterate a multi-level object, greetings.

    • 4

  4. I show you two alternatives that you can optimize according to your criteria to obtain the result you ask for.

    var obj = [{
		"seccion1": {
			"level1": {
				first: "John",
				last: "Doe"
			},
			"level2": {
				first: "juan",
				last: "perez"
			}
		}
	}];
	console.log('Opcion 1');
    //opcion 1
    obj.forEach(function(item) {
		Object.keys(item).forEach(function(key) {
			let value = item[key];
			Object.keys(value).forEach(function(key2) {
				console.log(key+ ' ' + key2 + ' ' + value[key2].first + ' ' + value[key2].last);
			});
		});
    });
	console.log('Opcion 2');
	//opcion 2
	obj.forEach(function(item) {
		Object.keys(item).forEach(function(key) {
			let value = item[key];
			let res = key;
			Object.keys(value).forEach(function(key2) {
				res = res + ' ' + key2 + ' ' + value[key2].first + ' ' + value[key2].last;
			});
			console.log(res);
		});
	});

    • 2