Adding additional element to an existing JSON array

Question

I have a case like, I want to add elements into a JSON array in TypeScript like below

[ 
{
"a" : "a1",
"b" : "b1"
}
]

Now I want to add values to the above object without creating new block, for example, I want to add key, value pair as "C": "c1" and "d": "d1". After doing this, my JSON array must look like below

[ 
{
"a" : "a1",
"b" : "b1"
"c" : "c1",
"d" : "d1"
}
]

What I tried:

let someData : any [] = [];

someData.push({
"a" : "a1",
"b" : b1"
})

someData.push({
"c" : "c1",
"d" : d1"
})

But it is creating two records like below, but this is wrong

[ 
{
"a" : "a1",
"b" : "b1"
}
{
"c" : "c1",
"d" : "d1"
}
]

as well I tried using unshift as below

someData.unshift({
"c" : "c1",
"d" : d1"
})

this is returning result object as

[ 
{
"a" : "a1",
"b" : "b1"
}
{
"c" : "c1",
"d" : "d1"
}
]

Is there any way to do?

For example,

for(int i =0; i<3; i++){
  someData.push({
    i : i+1
})

But the above block of code is creating wrong array structure, but inturn I want as below

{
0 :1,
1:2,
2:3
}
}

have you tried indexed interface in typescript ?

Pranay Rana
– Pranay Rana

2018-04-18 05:11:07 +00:00
Commented Apr 18, 2018 at 5:11 — Pranay Rana
– Pranay Rana, Commented Apr 18, 2018 at 5:11

Himanshu Bansal · Accepted Answer · 2018-04-18 05:57:27Z

3

Its supposed to be like this...

let someData : any [] = [];

someData.push({
"a" : "a1",
"b" : b1"
})

someData[0]["c"] = "c1";
someData[0]["d"] = "d1";

So when you log the values of someData ... it will show

console.log(someData); //[{"a":"a1","b" : "b1", "c":"c1", "d":"d1"}]

for looping through values...

let valuesToPut = [["c","c1"],["d","d1"]];

 for(let i = 0; i < valuesToPut.length; i++){
    someData[0][valuesToPut[i][0]] = valuesToPut[i][1]
 }

edited Apr 18, 2018 at 5:57

answered Apr 18, 2018 at 5:14

Himanshu Bansal

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2 Comments

user2000189 Over a year ago

This is partially working.. the case it does not work is when you try putting a for loop and use the values like below for(var i=0; i<3; i++){ someData[i]["c"] = "c1"; } in this case it is not working.

user2000189 Over a year ago

Sorry, i was mistaken in my for loop, now it is working fine.

Yanis-git · Accepted Answer · 2018-04-18 05:15:59Z

1

is little confusion between Object and Array, here you try to add some item to the Object who are store on index 0 of your array.

let try following code :

let someData : any [] = [];
// Create first index of array and create on it your Object.
someData.push({
    "a" : "a1",
    "b" : b1"
});

// Override first index of array by merge of previous data + new one.
someData[0] = Object.assign(someData[0], {
    "c1" : "c1",
    "d1" : "d1"
});

Object assign documentation

Another way to do this: Object.defineProperties()

answered Apr 18, 2018 at 5:15

Yanis-git

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Comments

Jihoon Kwon · Accepted Answer · 2018-04-18 05:22:51Z

1

As you mensioned, it is an array json format.

So, if you access some element in the array, you should indicate the array index.

ex:

let tempArray = [ 
{
"a" : "a1",
"b" : "b1"
}
]

=> tempArray[0] has this value.

{
"a" : "a1",
"b" : "b1"
}

So, if you add some additional values to the tempArray[0], you should access the element like below :

tempArray[0]['c'] = "c1";
tempArray[0]['d'] = "d1";

edited Apr 18, 2018 at 5:22

answered Apr 18, 2018 at 5:15

Jihoon Kwon

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Comments

kpie · Accepted Answer · 2018-04-18 05:27:55Z

//Let's start with what you're doing
let someData = [];

someData.push({
"a" : "a1",
"b" : "b1"
});
// pushes a collection of 2 key value pairs in as the first entry to someData
someData.push({
"c" : "c1",
"d" : "d1"
});
// pushes a collection of 2 key value pairs in as the second entry to someData
console.log(someData);

// what you might want to do:
someData = [];

someData.push({
"a" : "a1",
"b" : "b1"
});
// pushes a collection of 2 key value pairs in as the first entry to someData
someData[0].c = "c1";
//Sets a value to the key c in the first element of some data
someData[0].d = "d1";
//Sets a value to the key d in the first element of some data
console.log(someData)

// What you probably want to do.
someData = {};
for(let i of [1,2,3,4]){
  someData[String.fromCharCode(i+96)] = String.fromCharCode(i+96)+"1";
}
console.log(someData)

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