How to make a JSON object out of a dictionary? - javascript

I'me new to JavaScript. In the browser I receive a long dictionary like this:
{"cat": "4" , "dog": "5", "fish": "9" }
I'm wondering what is the most efficient way to convert it to a JSON object like:
[
{
"name": "cat",
"value": "4"
},
{
"name": "dog",
"value": "5"
},
{
"name": "fish",
"value": "9"
}
]

You can Loop through it and push each key-value-pair to an Array.
var tValue = {"cat": "4" , "dog": "5", "fish": "9" };
var tList = [];
for(var tKey in tValue) tList.push({name: tKey, value: tValue[tKey]});
console.log(tList);

You can just loop over the dictionary object keys using Object.keys() method, and use .map() method to transform each iterated key/value pair to the appropriate object:
var results = Object.keys(obj).map(function(k) {
return {
name: k,
value: obj[k]
};
});
Demo:
var obj = {
"cat": "4",
"dog": "5",
"fish": "9"
};
var results = Object.keys(obj).map(function(k) {
return {
name: k,
value: obj[k]
};
});
console.log(results);

You can use the function Object.entries to get every key-value pairs and with the function map build the desired output.
let obj = {"cat": "4" , "dog": "5", "fish": "9" },
result = Object.entries(obj).map(([name, value]) => ({name, value}));
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

You can do this by this way :
Call a for in loop and read your first object
Push the name and the value in your new object one by one..
Sample code :
var a = {"cat": "4" , "dog": "5", "fish": "9" };
var newJSON = [] ;
console.log(a);
for ( key in a ) {
newJSON.push({name : key, value : a[key]});
}
console.log(newJSON);

You can have this kind of formatted object
{
animals : [
{"name":"cat", "value": 4},
{"name":"dog", "value": 5},
{"name":"fish", "value": 9}
]
}
or like this
[
{"name":"cat", "value": 4},
{"name":"dog", "value": 5},
{"name":"fish", "value": 9}
]

Related

How to find multiple property values from an array of objects?

I have an array of objects like,
customer1 = [
{"key": "name",
"value": "Peter"},
{"key": "age",
"value": 23},
{"key": "address",
"value": "xyz St, abcd"},
{"key": "points",
"value": 234}
]
and I want to find say age and address from this object, what is the recommended and optimal way to do that? For real application, I might have 20-40 key-value objects in this array, out of which I might want to access 5-10 values.
What I do right now is I loop through this object and use conditions to find and assign values to my variables. but in this approach, I have to write multiple else if expressions (5-10).
For example,
let name: string;
let points: number;
for (var item of customer1) {
if (item.key === "name") {
name = item.value;
} else if (item.key === "points") {
points = item.value;
}};
You can simply achieve this requirement with the help of Array.filter() along with Array.map() method.
Live Demo :
const customer1 = [
{ "key": "name", "value": "Peter" },
{ "key": "age", "value": 23 },
{ "key": "address", "value": "xyz St, abcd" },
{ "key": "points", "value": 234 }
];
const searchKeys = ['age', 'address'];
const res = customer1.filter(obj => searchKeys.includes(obj.key)).map(({ value}) => value);
const [age, address] = res;
console.log(age);
console.log(address);
You will always have to write explicitly "name", "points",... because you can't parse string value and use it to identify variable with the same name.
But to avoid using multiple else if, maybe the switch case statement is more appropriate and readable?
interface CustomerProperty {
key: string,
value: string | number
}
let customer1: CustomerProperty[] = [
{
"key": "name",
"value": "Peter"
},
{
"key": "age",
"value": 23},
{
"key": "address",
"value": "xyz St, abcd"},
{
"key": "points",
"value": 234
}
];
let nameValue: string;
let pointsValue: number;
for (var item of customer1) {
switch (item.key) {
case "name":
nameValue = item.value as string;
break;
case "points":
pointsValue = item.value as number;
break;
}
};

How to .map correctly this array of objects?

I'm not sure what I'm doing wrong but I would like to map an array of objects. This array of objects it's dynamic, this means sometimes it has 4 objects and sometimes 20, so I need to make sure it will work no matters how many entries it has:
var obj = [
{
"key": "one",
"value": "something"
},
{
"key": "two",
"value": "random"
},
{
"key": "blue",
"value": "chicken"
},
{
"key": "orange",
"value": "sportsman"
}
];
I need to pass this objects into one to send it through a POST call that should match this format:
form: {
'one': 'something',
'two': 'random',
'blue': 'chicken',
'orange': 'sportsman'
}
I can access to item.value but IDK why I can't item.key:
var obj = [
{
"key": "one",
"value": "something"
},
{
"key": "two",
"value": "random"
},
{
"key": "blue",
"value": "chicken"
},
{
"key": "orange",
"value": "sportsman"
}
];
var combined = obj.map(function combined(item) {
return {
item.key: item.value
};
})
console.log(combined);
Any ideas? Thanks.
You shouldn't return an object from your callback function. Return an array of the key and value, then use Object.fromEntries() to turn this into a single object with those keys and values.
var obj = [{
"key": "one",
"value": "something"
},
{
"key": "two",
"value": "random"
},
{
"key": "blue",
"value": "chicken"
},
{
"key": "orange",
"value": "sportsman"
}
];
var combined = Object.fromEntries(obj.map(item => [item.key, item.value]));
console.log(combined);
1) You can't use a map here because the map will return a new array. You can achieve this result using reduce
var obj = [
{
key: "one",
value: "something",
},
{
key: "two",
value: "random",
},
{
key: "blue",
value: "chicken",
},
{
key: "orange",
value: "sportsman",
},
];
const result = obj.reduce((acc, curr) => {
const { key, value } = curr;
acc[key] = value;
return acc;
}, {});
console.log(result);
2) You can also do this using for..of loop
var obj = [{
key: "one",
value: "something",
},
{
key: "two",
value: "random",
},
{
key: "blue",
value: "chicken",
},
{
key: "orange",
value: "sportsman",
},
];
const result = {};
for (let o of obj) {
result[o.key] = o.value;
}
console.log(result);

Getting the key in every JSON object

I am fairly new to Vue and JS but I am making API calls and getting a JSON response then sending the response to an empty array. How do I get the ID of each object in the array?
The array that the response is being pushed to is structured like this
groups: [
{
"id": "0",
"name": "a",
"price": 5
},
{
"id": "1",
"name": "b",
"price": 5
},
{
"id": "2",
"name": "c",
"price": 5
}
]
I'd like to pull the Id of each object and push the values to an empty array
for(var group in this.groups) {
if (this.groups.hasOwnProperty(0)) {
this.group = this.groups[0];
this.groupsId.push(this.innerObj);
}
}
The error I'm getting is saying Cannot read property '0' of undefined at eval
Ideally I'd like an array that has all the Ids of each object.
this.groups.hasOwnProperty(0) should be group.hasOwnProperty('id')
Use Array.prototype.map() to iterate over an array of objects and collect every ID into a new array:
const res = {
groups: [{
"id": "0",
"name": "a",
"price": 5
},
{
"id": "1",
"name": "b",
"price": 5
},
{
"id": "2",
"name": "c",
"price": 5
}
]
};
const ids = res.groups.map(obj => { // you use this.groups
if(obj.hasOwnProperty('id')) return obj.id;
});
console.log(ids)
There is the Array.map() method:
this.groupsId = this.groups.map(i => i.id);
If you already have elements in this.groupsId you can append the ids using Array.concat():
this.groupsId = this.groupsId.concat(this.groups.map(i => i.id));
You can use Array.prototype.reduce to loop and check if there's id.
const groups = [
{"name": "a","price": 5},
{"id": "1","name": "b","price": 5},
{ "id": "2","name": "c","price": 5}
];
const list = groups.reduce((groupIds, group) => group.id ? [...groupIds, group.id] : groupIds, []);
console.log(list);

How to merge multiple object arrays into one array cross with sub array?

I have two arrays of objects:
1)
[
{
"userId": 9
},
{
"userId": 14
}
]
2)
[{"role": "1", "group": "3"}, {"role": "1", "group": "2"}]
I would like to merge two arrays as follows:
[
{"userId":9,"role":"1","group":"2"},
{"userId":14,"role":"1","group":"2"}
{"userId":9,"role":"1","group":"3"},
{"userId":14,"role":"1","group":"3"}
]
I tried to use let however I couldn't find the way to manipulate switch the subarray :
let arr1 = [{"userId": 9}, {"userId": 14}];
let arr2 = [{"role": "1", "group": "3"}, {"role": "1", "group": "2"}];
let result = arr1.map(o => Object.assign(o, ...arr2));
console.log(result);
return result;
The result I got with the previous implementation is like this :
[{"userId":9,"role":"1","group":"2"},{"userId":14,"role":"1","group":"2"}]
However, I would like to get the result as follows :
[
{"userId":9,"role":"1","group":"2"},
{"userId":14,"role":"1","group":"2"}
{"userId":9,"role":"1","group":"3"},
{"userId":14,"role":"1","group":"3"}
]
var a = [{
"userId": 9
},
{
"userId": 14
}
]
var b = [{
"role": "1",
"group": "3"
}, {
"role": "1",
"group": "2"
}]
console.log(
b.map(z=>a.map(x=>({...x, ...z}))).flat()
)
Another solution using for loop
let arr1 = [{ "userId": 9 }, { "userId": 14 }]
let arr2 = [{"role": "1","group": "3"}, {"role": "1","group": "2" }]
let result = [];
for (let group of arr2) {
for (let user of arr1) [
result.push(Object.assign({}, group, user))
]
}
console.log(JSON.stringify(result))
//output is:
// [
// {"role":"1","group":"3","userId":9},
// {"role":"1","group":"3","userId":14},
// {"role":"1","group":"2","userId":9},
// {"role":"1","group":"2","userId":14}
// ]
Stackblitz example
To achieve expected result, use below option of looping through two arrays
var x = [
{
"userId": 9
},
{
"userId": 14
}
]
var y = [{"role": "1", "group": "3"}, {"role": "1", "group": "2"}]
let result = []
y.forEach((v, i) =>{
x.forEach((y,i) => result.push({...v, ...y}))
})
console.log(result);
codepen - https://codepen.io/nagasai/pen/pxvzOG?editors=1010
You could iterate over the two arrays like this and push the merged values into result:
arr1.forEach(e => {
arr2.forEach(e2 => {
result.push(Object.assign({}, e, e2));
});
});
Which could also be written in ONE LINE:
arr1.forEach(e => arr2.forEach(e2 => result.push(Object.assign({}, e, e2))));
const arr1 = [{
"userId": 9
},
{
"userId": 14
}
];
const arr2 = [{
"role": "1",
"group": "3"
}, {
"role": "1",
"group": "2"
}];
const result = [];
arr1.forEach(e => {
arr2.forEach(e2 => {
result.push(Object.assign({}, e, e2));
});
});
console.log(result);
You can use a mix a reduce and map to boil it down to a single array of objects.
let data = [{
"userId": 9
},
{
"userId": 14
}
]
let metaData = [{
"role": "1",
"group": "3"
}, {
"role": "1",
"group": "2"
}];
let dataReducer = data.reduce((acc, curr) => {
let metadataReducer = metaData.map((val) => {
return {
...curr,
...val
};
}, []);
return [...acc, ...metadataReducer];
}, []);
console.log(dataReducer)
Here a short approach for an arbitrary count of arrays of objects.
var array1 = [{ userId: 9 }, { userId: 14 }],
array2 = [{ role: "1", group: "3" }, { role: "1", group: "2" }],
result = [array1, array2]
.reduce((a, b) =>
a.reduce((r, v) =>
r.concat(b.map(w => Object.assign({}, v, w))), []));
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }
You're basically asking for a Cartesian product of the two arrays. flatMap is a useful function here. For each element of one array, merge it with all objects from the other array, then return a flat result.
const a = [{userId: 9}, {userId: 14}];
const b = [{role: "1", group: "3"}, {role: "1", group: "2"}];
const merged = b.flatMap(ae => a.map(be => ({...be, ...ae})));
console.log(merged);

Change representation of JSON object to explicit key/value format

I have the following JSON:
{
"temperature": "22.2",
"power": "6",
"current": "156"
}
and I need to convert it to this explicit structure:
{
"key": "temperature",
"value": "22.2"
},
{
"key": "power",
"value": "6"
},
{
"key": "current",
"value": "156"
}
Is there an elegant, simple and quick way to do this?
Best, thx
var newStructure = Object.keys(obj).map(function(key){
return {'key':key, 'value':obj[key]}
})
Example
var obj = {
"temperature": "22.2",
"power": "6",
"current": "156"
}
var arr = Object.keys(obj).map(function(key){return {'key':key,'value':obj[key]}})
console.log(arr)
Object.hashToKeyValuePairs = function (hash) {
var ret = [];
for (var i in hash)
ret.push({ key: i, value: hash[i]});
return ret;
};
// example
document.body.innerHTML = JSON.stringify(
Object.hashToKeyValuePairs({ a: 1, b: 2, c: 3 })
);

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