CODEWITHSUNDEEP
javascriptarraysobjectdata-structures
paynestrike
paynestrike

Reputation: 4658

How to update an array of object in javascript

say I have a variable 

 data=[] 

 //this variable is an array of object like 
 data = [
     {name:'a',value:'aa'},
     {name:'b',value:'bb'}
 ]

 // the data structrue can not be changed and the initial value is empty

now I want to update the data

 function updateData(){
     if(!data.length){
         data.push(arguments)
     }
     else{
         //this parts really confuse me
     }

 }

this function must accept any number of arguments,and the order of the objects in data dose not matters update rule:

  1. update the objects value to the arguments value if they have the same name.
  2. add the arguments to the data if none of the object in data have the same name.

how to write this function?

 updateData([
     {name:'a',value:'aa'},
     {name:'b',value:'bb'}
 ])
 // expect data = [
           {name:'a',value:'aa'},
           {name:'b',value:'bb'}
           ]

 updateData([
     {name:'a',value:'aa'},
     {name:'b',value:'DD'},
     {name:'c',value:'cc'}
] )
 // expect data = [
           {name:'a',value:'aa'},
           {name:'b',value:'DD'},
           {name:'c',value:'cc'}
           ]

Upvotes: 3

Views: 60381

Answers (4)

Ashutosh Upadhyay
Ashutosh Upadhyay

Reputation: 481

Since order doesn't really matter to you, better choice would be an object hash instead of an array. Something like

{
  'a':{name:'a', value: 'aa'}
}

This will let you search easily based on keys and you can update the hash.

You can even employ above to your situation. Convert the array into a temporary object hash as above, do necessary changes, and convert back to an array. This will be more efficient as it will save you searches through the array.

 var output_array = [];
 for (var key in obj) {
   if (obj.hasOwnProperty(key)) {
      output_array.push(obj[key]);
   }
 }

Upvotes: 1

HMR
HMR

Reputation: 39270

As Ashutosh Upadhyay suggested use a name value pair instead of an array:

var data ={};

var updateData=function(){
  var len = arguments.length,
  i=0;
  for(i=0;i<len;i++){
    data[arguments[i].name]=arguments[i].value;
  }
};
updateData(
 {name:"a",value:"22"}, 
 {name:"b",value:"2"}, 
 {name:"c",value:"3"}, 
 {name:"a",value:"1"} // the new value for a
);
for(key in data){
  if(data.hasOwnProperty(key)){
    console.log(key + "=" + data[key]);
  }
}

Just read your comment about the array, so if you have to have an array you can:

var data = [];
function findIndex(name){
  var i = 0;
  for(i=0;i<data.length;i++){
    if(data[i].name===name){
      return i;
    }
  }
  return i;
}
function updateData(){
  var i = 0;
  for(i=0;i<arguments.length;i++){
    data[findIndex(arguments[i].name)]=arguments[i];
  }
}
updateData(
 {name:"a",value:"22"}, 
 {name:"b",value:"2"}, 
 {name:"c",value:"3"}, 
 {name:"a",value:"1"} // the new value for a
);

console.log(data);

Upvotes: 2

Pablo Lozano
Pablo Lozano

Reputation: 10342

if names are unique you could define data as a map and just add the values using the name as key:

 var data={
     'a':'aa',
     'b':'bb'
 }

function updateData() {
   for (var i=0;i<arguments.length;i++) { //for each argument...
      for (key in arguments[i]) { //we'll put each pair (key,value) in the data
         data[key]=arguments[i][key];
      }
   }

}

EDIT: function to transform to an array

 function toArray() {
    var array=[];
    for (key in data) {
       array.push({name:key,value:data[key]});
    }
    return array;
 }

Upvotes: 1

Romaindr
Romaindr

Reputation: 311

Ok you might want to do something like that?

var data = [
     {name:'a',value:'aa'},
     {name:'b',value:'bb'}
 ];

 function updateData(obj){
  var objFound_bool = false;
  for (var i = 0; i < data.length; i++) {
    if(obj.name === data[i].name){
      objFound_bool = true;
      data[i].value =obj.value ;
    }
  }
  if(!objFound_bool){
    data.push(obj)
  }
 }

Upvotes: 4

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