How to convert an array to an object, and how to convert an object to an array

Catalog

One 、 How to convert an array to an object

Two 、 Object to array

3、 ... and 、 Mutual conversion is encapsulated into functions

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One 、 How to convert an array to an object

1、 demand

let arr = [{label: ' male ', value: 0},{label: ' Woman ', value: 1}]
//  Convert to  
let obj = {0:' male ', 1:' Woman '}

2、 Realization

Train of thought ：

1. array-based forEach Method traverses the array
2. Define an empty object
3. Will iterate through each of the resulting objects value Be worthy of being a new object key,label As the value of the new object
4. At the end of the cycle obj The value of is returned to the caller

let arr = [{label: ' male ', value: 0},{label: ' Woman ', value: 1}]

function arrToObj(arr){
    let obj = {}
    arr.forEach(item => {
        obj[item.value] = item.label
    })
    return obj
}

const obj1 = arrToObj(arr)
console.log(' Array forEach Method ', obj1)

Train of thought two ：

1. array-based forEach Method traverses the array
2. Define an empty object
3. Will iterate through each of the resulting objects value Be worthy of being a new object key,label As the value of the new object
4. At the end of the cycle obj The value of is returned to the caller

let arr = [{label: ' male ', value: 0},{label: ' Woman ', value: 1}]

function arrToObj1(arr){
   return arr.reduce((obj,item) => {
        obj[item.value] = item.label
    	return obj
    },{})
}

const obj2 = arrToObj1(arr)
console.log(' Array reduce Method ', obj2)

Two 、 Object to array

1. demand

let obj = { 0: ' male ', 1: ' Woman ' }
//  Convert to 
let arr = [{label: ' male ', value: 0},{label: ' Woman ', value: 1}]

2. Realization

let obj = { 0: ' male ', 1: ' Woman ' }

//  Use for...in... loop , Get the key of the object 、 value 
//  Make it a new object , array-based push Method is appended to the array 
function objToArr(obj){
    let arr = []
    for(let key in obj){
        arr.push({
            label: obj[key],
            value: key
        })
    }
    return arr
}

const arr = objToArr(obj)
console.log(arr)

3、 ... and 、 Mutual conversion is encapsulated into functions

//  Array to object 、 Object to array 
function arr_obj(query) {
  //  If the parameter is not passed , It is assigned as  undefined
  this.query = query || undefined;
  this.params = this.query;

  //  Default object 
  var defaultObj = {};
  //  The default array 
  var defaultArr = [];
  //  Array to object 
  this.arrToObj = function(arr) {
    var obj = {}
    for (var i = 0; i < arr.length; i++) {
      //  Array to object , Object's key = Array value ,  The value of the object = Array value 
      obj[arr[i]] = arr[i];
      //  If it's an array , Call itself again  (this.arrToObj), Recursion followed by loop 
      if (Object.prototype.toString.call(arr[i]) == "[object Array]") {
        var deepArray = this.arrToObj(arr[i])
        continue;
      } else {
        defaultObj[arr[i]] = arr[i]
      }
    }
    this.params = defaultObj;
  };

  //  Object to array 
  this.objToArr = function(obj) {
    var arr = [];
    for (var i in obj) {
      arr.push(obj[i]);
      //  If it's an object , Call itself again  (this.ObjToObj), Recursion followed by loop 
      if(Object.prototype.toString.call(obj[i]) == "[object Object]"){
        var deepObject=this.objToArr(obj[i]);
        continue;
      }else{
        defaultArr.push(obj[i])
      }
    }
    this.params = defaultArr;
  };

  if (Object.prototype.toString.call(this.query) == "[object Array]") {
    this.arrToObj(this.query);
  } else if (Object.prototype.toString.call(this.query) == "[object Object]") {
    this.objToArr(this.query);
  } else if (Object.prototype.toString.call(this.query) == "[object Undefined]") {
    console.error(" The parameter passed in was not obtained ", this.params);
    throw " The parameter passed in was not obtained "
  } else {
    console.error(" Wrong parameters :", this.params,
      " Wrong parameter type :", Object.prototype.toString.call(this.params));
    throw " The parameters passed can only be object or array types "
  }
  return this.params;
}
//  call   Object to array 
var obj = {
  a1:"a",
  b1:{
    c1:"c",d1:"d"
    ,q1:{
      q:"q",w:"w",
    },
  },
  e1:"e",
  f1:"f"
  };
// //  call   Array to object 
var arr = ["a", ["c",["e"],"q"],"t"];
var asd1 = new arr_obj(arr);
console.log(asd1);
//  Output  {a: "a", c: "c", e: "e", q: "q", t: "t"}
//  call   Object to array 
var asd2=new arr_obj(obj);
console.log(asd2);
//  Output   ["a", "c", "d", "q", "w", "e", "f"]