How to create an array of objects from a 2d array in javascript?

Question

This is similar to my real problem, but I feel that this is a problem that I need to solve without complicating the situation.

I need to create an array of objects, iterating through a 2d array. The 2d array looks something like “sampleArray” below.

let sampleArray = [ 
  ["open",2], 
  ["high",3], 
  ["low",5], 
  ["close", 10], 
  ["volume", 20], 
  ["open",20], 
  ["high",30], 
  ["low",50], 
  ["close", 100], 
  ["volume", 21],
  ["open",21], 
  ["high",33], 
  ["low",51], 
  ["close", 1], 
  ["volume", 2],
  ["open",7], 
  ["high",8], 
  ["low",5], 
  ["close", 11], 
  ["volume", 22]
 ];

I am currently formatting an especially ugly API dataset and smoothing data to a 2-dimensional array. Now I need to put these values ​​in an array of 5 objects, where each property of the object’s data is filled with all the values ​​of this particular label.

newObject = [
    {
     data: [2,20,21, ...]
     label: "open"  
    }, 
    {
     data: [3,50, ...]
     label: "high"
    }, 
    {
     data: [etc...]
     label: "low"  
    }, 
    {
     data: [etc...]
     label: "close"  
     }, 
    {
     data: [etc...]
     label: "volume"  
     }
]

3 , , , , newArray [i] [ "label" ] undefined, , ( YET, , ( , value) javascript.

function makeArray(array) {
  let newArray = [];
  for(let i = 0; i <= array.length; i++){
    if(newArray[i]["label"] !== array[i][0]){
      newArray.push({
        "label": array[i][0],
        "value": array[i][1]
      })
    }    
    else{
      newArray.push({
        "value": array[i][1]
      })
    }
  }
return newArray;
}

let test = makeArray(sampleArray);
console.log(test);

, API , . , . , - . !

Answer 1

reduce

let sampleArray = [
  ["open", 2],
  ["high", 3],
  ["low", 5],
  ["close", 10],
  ["volume", 20],
  ["open", 20],
  ["high", 30],
  ["low", 50],
  ["close", 100],
  ["volume", 21],
  ["open", 21],
  ["high", 33],
  ["low", 51],
  ["close", 1],
  ["volume", 2],
  ["open", 7],
  ["high", 8],
  ["low", 5],
  ["close", 11],
  ["volume", 22]
];


let newObject = Object.values(sampleArray.reduce((c, [n, v]) => {
  c[n] = c[n] || {label: n,data: []};
  c[n].data.push(v);
  return c;
}, {}));

console.log(newObject);

Hide result

Answer 2

Vanilla JS:

let sampleArray = [
  ["open", 2],
  ["high", 3],
  ["low", 5],
  ["close", 10],
  ["volume", 20],
  ["open", 20],
  ["high", 30],
  ["low", 50],
  ["close", 100],
  ["volume", 21],
  ["open", 21],
  ["high", 33],
  ["low", 51],
  ["close", 1],
  ["volume", 2],
  ["open", 7],
  ["high", 8],
  ["low", 5],
  ["close", 11],
  ["volume", 22]
];

function transform(sampArr) {
  let obj = {};                                 // A map equivalent to store repeated value
  
  // Loop through each array within array
  sampArr.forEach(function(arr) {
    if (!obj[arr[0]]) {
      obj[arr[0]] = {};                         // Instantiate the map the first time
    }

    if (!obj[arr[0]].data) {
      obj[arr[0]]["data"] = [];                 // First time instantiate the array
    }

    obj[arr[0]].data.push(arr[1]);              // Push the repeated values
  });


  // Create the structure you want
  return Object.keys(obj).map(function(key) {
    return {
      data: obj[key].data,
      label: key
    };
  });
}

console.log(transform(sampleArray));

Hide result

Answer 3

-

const tempObject = sampleArray.reduce((acc, arr) => {
  if (acc.hasOwnProperty(arr[0]) {
    return acc[arr[0]].push(arr[1]);
  }
  return { ...acc, { [arr[0]]: [arr[1]] };
}), {});

tempObject -

{
  'open': [2, 20, 21, ...],
  'high': [3, 50, ...],
  'low': [etc, ...],
  'close': [etc, ...],
  'volume': [etc, ...]
}

eterate ,

const finalData = Object.keys(tempObject).map(key => (
  {
    data: tempObject[key],
    label: key
  }
);

Now finalData strong> will be desired.