How to update an array of object in javascript

Question

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:

update the objects value to the arguments value if they have the same name.
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'}
           ]

you missed a comma between {name:'a',value:'aa'} and {name:'b',value:'bb'} at many places — Moazzam Khan
– Moazzam Khan, Commented Jul 19, 2013 at 8:01
Its a real project question, I need to dynamiclly add jquery file upload's formData — paynestrike
– paynestrike, Commented Jul 19, 2013 at 8:03

Romaindr · Accepted Answer · 2013-07-19 08:07:37Z

4

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)
  }
 }

answered Jul 19, 2013 at 8:07

Romaindr

3111 silver badge7 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

HMR Over a year ago

You can just break if the if statemnet is true and after the for loop do data[i]=obj;

paynestrike Over a year ago

please note that the updateData function must accept any number of argument and tha initial value of data is empty

Learner Over a year ago

Hi, I have a similar scenario and can you help on it please?

HMR · Accepted Answer · 2013-07-19 08:29:05Z

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);

Pablo Lozano · Accepted Answer · 2013-07-19 08:22:39Z

1

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;
 }

edited Jul 19, 2013 at 8:22

answered Jul 19, 2013 at 8:03

Pablo Lozano

10.4k2 gold badges43 silver badges64 bronze badges

6 Comments

paynestrike Over a year ago

like I said the variable's data structrue can not be changed, if you have to change it to make the function easier then you have to change it back

Pablo Lozano Over a year ago

sorry, I forgot that part.. here it is now

paynestrike Over a year ago

I tried your function and Its wrong (var key in arguments[i]),this is wrong

Pablo Lozano Over a year ago

Are you sure? I've C&P that code in the Chrome and Firefox (Firebug) consoles and it worked in both browsers.

paynestrike Over a year ago

the updateDate() function is right but the toArray function is wrong; it will output something like [{name:'name','value':'a'},{name:'value',value:'aa'}]

|

Ashutosh Upadhyay · Accepted Answer · 2013-07-19 08:34:07Z

1

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]);
   }
 }

edited Jul 19, 2013 at 8:34

answered Jul 19, 2013 at 8:03

Ashutosh Upadhyay

4913 silver badges6 bronze badges

1 Comment

paynestrike Over a year ago

this is what I have in mind, but It seems even harder to convert the object back to array, can you give me an example

Collectives™ on Stack Overflow

How to update an array of object in javascript

4 Answers 4

3 Comments

Comments

6 Comments

1 Comment

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

3 Comments

Comments

6 Comments

1 Comment

Related