This question already has answers here:
One liner to flatten nested object
(19 answers)
Closed 1 year ago.
I am trying to achieve it Like a:1,b:2:,c:3,e:4,g:5,h:6
But not getting success.
Facing error this. But is the best way to do it.
const input = {
a: 1,
b: 2,
c: 3,
d: {
e: 4,
f: {
g: 5,
h: 6
}
}
}
const getValue = (values) => {
for (let i in Object.keys(values)) {
if (Object.keys(values[Object.keys(values)[i]]).length > 0) {
console.log('v', Object.keys(values)[i])
getValue(Object.keys(values)[i])
} else {
// console.log(Object.keys(values)[i],Object.values(values)[i])
}
}
}
getValue(input)
You can iterate through each key of object and for object value recursively call your getValue() function.
const input = { a:1, b:2, c:3, d:{ e:4, f:{ g:5, h:6 } } }
const getValue = (values) => {
for (const key of Object.keys(values)) {
if(typeof values[key] === 'object' && values[key] !== null) {
getValue(values[key]);
} else {
console.log(`${key}: ${values[key]}`);
}
}
}
getValue(input);
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You could use recursion to get the desired result.
const input = {
a: 1,
b: 2,
c: 3,
d: {
e: 4,
f: {
g: 5,
h: 6,
},
},
};
const result = {};
function getValues(obj) {
for (let key in obj) {
if (typeof obj[key] !== `object`) result[key] = obj[key];
else getValues(obj[key]);
}
}
getValues(input);
console.log(result);
Edited : you can do something like this
const input = {a:1,b:2,c:3,d:{e:4,f:{g:5,h:6 }}}
Object.assign({}, ...function _flatten(o) { return [].concat(...Object.keys(o).map(k => typeof o[k] === 'object' ? _flatten(o[k]) : ({[k]: o[k]})))}(input))
//{a: 1, b: 2, c: 3, e: 4, g: 5, …}
you can see more details here
This question already has answers here:
Object comparison in JavaScript [duplicate]
(10 answers)
Closed 1 year ago.
How can i compare 2 objects and their values using ES6?
Objects i have:
let obj1 = { c: 1, o: 1, m: 2, a: 1, s: 1 }
let obj2 = { a: 4, b: 2, c: 3, m: 2, o: 1, s: 1, d: 2 }
I want to check if obj1[key] exists in obj2. And if value of this key in obj2 same as in obj1 return true;
PS i'm kinda new to programming
I made a simple mockup with "pseudocode" comment that should help you understand
function checkObjInTables(tab1, tab2, key){
// return {KEY EXIST IN TABLE 1} AND {KEY EXIST IN TABLE 2} AND {VALUE OF KEY IN TABLE 1} IS EQUAL TO {VALUE OF KEY IN TABLE 2}
return key in tab1 && key in tab2 && tab1[key] == tab2[key];
};
let obj1 = { c: 1, o: 1, m: 2, a: 1, s: 1 }
let obj2 = { a: 4, b: 2, c: 3, m: 2, o: 1, s: 1, d: 2 }
console.log(checkObjInTables(obj1, obj2, "s")); // true
console.log(checkObjInTables(obj1, obj2, "a")); // false
Assuming the objects in the example above are not equal and that the definition of "equal" above is incomplete (and assuming we want to handle objects only) the following should work:
function equals(o1, o2) {
if (typeof o1 !== 'object' || typeof o2 !== 'object') {
return false; // we compare objects only!
}
// when one object has more attributes than the other - they can't be eq
if (Object.keys(o1).length !== Object.keys(o2).length) {
return false;
}
for (let k of Object.keys(o1)) {
if (o1[k] !== o2[k]) {
return false;
}
}
return true;
}
To clarify, according to the definition in the question the following objects are equal:
o1 = { a: 1 };
o2 = { a: 1, b: 2 };
but I find it hard to believe that this was the intention of the OP!
There is a JavaScript way.
let obj1 = { c: 1, o: 1, m: 2, a: 1, s: 1 };
let obj2 = { a: 4, b: 2, c: 3, m: 2, o: 1, s: 1, d: 2 };
const isObject = obj => typeof obj === 'object' && obj !== null;
function check(obj1, obj2) {
// check if both inputs are object and not null
if(!isObject(obj1) || !isObject(obj2)) return false;
// check if both obj has equal size
if(Object.keys(obj1) !== Object.keys(obj2)) return false;
for (const key of Object.keys(obj1)) {
if (!(key in obj2) || obj1[key] !== obj2[key]) return false;
}
return true;
}
console.log(check(obj1, obj2));
Implement the sumObjects function, which takes an unlimited number of objects and returns an object that combines all the objects entered.
Notes:
All object properties will have numeric values only
If the object keys match, the values of the corresponding keys are summed
The function always returns an object
The numbers in the object can be positive or negative
You can use the rest operator to collect arguments passed to a function in one array
Examples:
const obj = {};
sumObjects() === {}
sumObjects(obj) === {}
and
const first = {a: 2, b: 4};
const second = {a: 2, b: 10};
const third = {d: -5};
sumObjects(first) === {a: 2, b: 4}
sumObjects(first, third) === {a: 2, b: 4, d: -5}
sumObjects(first, second, third) === {a: 4, b: 14, d: -5}
This is my code.
function sumObjects(...params) {
let C = Object.fromEntries(
Object.keys(params[0])
.concat(Object.keys(params[1]))
.map(k => [k,
(params[0][k] || 0) + (params[1][k])
])
)
return C
}
I don't know how to add all these objects into one.
The bottom line is that I need to combine all the objects, but I just don't know how to do this, I can't find anything.
You can iterate over the param objects using .reduce and for each object, set/update its properties in acc:
function sumObjects(...params) {
return params.reduce((acc,item) => {
Object.entries(item).forEach(([property,value]) => {
const prev = acc[property];
acc[property] = prev ? prev+value : value;
});
return acc;
}, {});
}
const first = { a: 2, b: 4 };
const second = { a: 2, b: 10 };
const third = { d: -5 };
console.log( sumObjects(first) );
console.log( sumObjects(first, third) );
console.log( sumObjects(first, second, third) );
You could reduce the array of objects and iterate the entries of a single object.
const
sumObjects = (...objects) => objects.reduce((r, o) => {
Object.entries(o).forEach(([k, v]) => r[k] = (r[k] ||0) + v);
return r;
}, {}),
first = { a: 2, b: 4 },
second = { a: 2, b: 10 },
third = { d: -5 };
console.log(sumObjects(first)); // {a: 2, b: 4}
console.log(sumObjects(first, third)); // {a: 2, b: 4, d: -5}
console.log(sumObjects(first, second, third)); // {a: 4, b: 14, d: -5}
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This question already has answers here:
Find object by id in an array of JavaScript objects
(36 answers)
Closed 4 years ago.
Let's say I have an array of four objects:
var jsObjects = [
{a: 1, b: 2},
{a: 3, b: 4},
{a: 5, b: 6},
{a: 7, b: 8}
];
Is there a way that I can get the third object ({a: 5, b: 6}) by the value of the property b for example without a for...in loop?
Filter array of objects, which property matches value, returns array:
var result = jsObjects.filter(obj => {
return obj.b === 6
})
See the MDN Docs on Array.prototype.filter()
const jsObjects = [
{a: 1, b: 2},
{a: 3, b: 4},
{a: 5, b: 6},
{a: 7, b: 8}
]
let result = jsObjects.filter(obj => {
return obj.b === 6
})
console.log(result)
Find the value of the first element/object in the array, otherwise undefined is returned.
var result = jsObjects.find(obj => {
return obj.b === 6
})
See the MDN Docs on Array.prototype.find()
const jsObjects = [
{a: 1, b: 2},
{a: 3, b: 4},
{a: 5, b: 6},
{a: 7, b: 8}
]
let result = jsObjects.find(obj => {
return obj.b === 6
})
console.log(result)
jsObjects.find(x => x.b === 6)
From MDN:
The find() method returns a value in the array, if an element in the array satisfies the provided testing function. Otherwise undefined is returned.
Side note: methods like find() and arrow functions are not supported by older browsers (like IE), so if you want to support these browsers, you should transpile your code using Babel.
I don't know why you are against a for loop (presumably you meant a for loop, not specifically for..in), they are fast and easy to read. Anyhow, here's some options.
For loop:
function getByValue(arr, value) {
for (var i=0, iLen=arr.length; i<iLen; i++) {
if (arr[i].b == value) return arr[i];
}
}
.filter
function getByValue2(arr, value) {
var result = arr.filter(function(o){return o.b == value;} );
return result? result[0] : null; // or undefined
}
.forEach
function getByValue3(arr, value) {
var result = [];
arr.forEach(function(o){if (o.b == value) result.push(o);} );
return result? result[0] : null; // or undefined
}
If, on the other hand you really did mean for..in and want to find an object with any property with a value of 6, then you must use for..in unless you pass the names to check.
Example
function getByValue4(arr, value) {
var o;
for (var i=0, iLen=arr.length; i<iLen; i++) {
o = arr[i];
for (var p in o) {
if (o.hasOwnProperty(p) && o[p] == value) {
return o;
}
}
}
}
Ways to achieve the requirement :
Using Array.find() method :
const jsObject = [
{a: 1, b: 2},
{a: 3, b: 4},
{a: 5, b: 6},
{a: 7, b: 8}
];
const filteredResult = jsObject.find((e) => e.b == 6);
console.log(filteredResult);
Using Array.filter() method :
const jsObjects = [
{a: 1, b: 2},
{a: 3, b: 4},
{a: 5, b: 6},
{a: 7, b: 8}
];
const filterObj = jsObjects.filter((e) => e.b == 6);
console.log(filterObj[0]);
Using for...in loop :
const jsObjects = [
{a: 1, b: 2},
{a: 3, b: 4},
{a: 5, b: 6},
{a: 7, b: 8}
];
for (const i in jsObjects) {
if (jsObjects[i].b == 6) {
console.log(jsObjects[i]);
}
}
OK, there are few ways to do that, but let's start with the simplest one and latest approach to do this, this function is called find().
Just be careful when you using find to as even IE11 dosn't support it, so it needs to be transpiled...
so you have this object as you said:
var jsObjects = [
{a: 1, b: 2},
{a: 3, b: 4},
{a: 5, b: 6},
{a: 7, b: 8}
];
and you can write a function and get it like this:
function filterValue(obj, key, value) {
return obj.find(function(v){ return v[key] === value});
}
and use the function like this:
filterValue(jsObjects, "b", 6); //{a: 5, b: 6}
Also in ES6 for even shortened version:
const filterValue = (obj, key, value)=> obj.find(v => v[key] === value);
This method only return the first value which match..., for better result and browser support, you can use filter:
const filterValue = (obj, key, value)=> obj.filter(v => v[key] === value);
and we will return [{a: 5, b: 6}]...
This method will return an array instead...
You simpley use for loop as well, create a function like this:
function filteredArray(arr, key, value) {
const newArray = [];
for(i=0, l=arr.length; i<l; i++) {
if(arr[i][key] === value) {
newArray.push(arr[i]);
}
}
return newArray;
}
and call it like this:
filteredArray(jsObjects, "b", 6); //[{a: 5, b: 6}]
See this documentation Array.prototype.find()
Example:
var inventory = [
{name: 'apples', quantity: 2},
{name: 'bananas', quantity: 0},
{name: 'cherries', quantity: 5}
];
function findCherries(fruit) {
return fruit.name === 'cherries';
}
console.log(inventory.find(findCherries));
// { name: 'cherries', quantity: 5 }
Using underscore.js:
var foundObject = _.findWhere(jsObjects, {b: 6});
It looks like in the ECMAScript 6 proposal there are the Array methods find() and findIndex(). MDN also offers polyfills which you can include to get the functionality of these across all browsers.
find():
function isPrime(element, index, array) {
var start = 2;
while (start <= Math.sqrt(element)) {
if (element % start++ < 1) return false;
}
return (element > 1);
}
console.log( [4, 6, 8, 12].find(isPrime) ); // undefined, not found
console.log( [4, 5, 8, 12].find(isPrime) ); // 5
findIndex():
function isPrime(element, index, array) {
var start = 2;
while (start <= Math.sqrt(element)) {
if (element % start++ < 1) return false;
}
return (element > 1);
}
console.log( [4, 6, 8, 12].findIndex(isPrime) ); // -1, not found
console.log( [4, 6, 7, 12].findIndex(isPrime) ); // 2
If I understand correctly, you want to find the object in the array whose b property is 6?
var found;
jsObjects.some(function (obj) {
if (obj.b === 6) {
found = obj;
return true;
}
});
Or if you were using underscore:
var found = _.select(jsObjects, function (obj) {
return obj.b === 6;
});
If you are looking for a single result, rather than an array, may I suggest reduce?
Here is a solution in plain 'ole javascript that returns a matching object if one exists, or null if not.
var result = arr.reduce(function(prev, curr) { return (curr.b === 6) ? curr : prev; }, null);
You can use it with the arrow function as well like as below :
var demoArray = [
{name: 'apples', quantity: 2},
{name: 'bananas', quantity: 0},
{name: 'cherries', quantity: 5}
];
var result = demoArray.filter( obj => obj.name === 'apples')[0];
console.log(result);
// {name: 'apples', quantity: 2}
How about using _.find(collection, [predicate=_.identity], [fromIndex=0]) of lo-dash to get object from array of objects by object property value. You could do something like this:
var o = _.find(jsObjects, {'b': 6});
Arguments:
collection (Array|Object): The collection to inspect.
[predicate=_.identity] (Function): The function invoked per iteration.
[fromIndex=0] (number): The index to search from.
Returns
(*): Returns the matched element (in your case, {a: 5, b: 6}), else undefined.
In terms of performance, _.find() is faster as it only pulls the first object with property {'b': 6}, on the other hand, if suppose your array contains multiple objects with matching set of properties (key:value), then you should consider using _.filter() method. So in your case, as your array has a single object with this property, I would use _.find().
Made the best/fastest part of this answer more re-usable & clear:
function getElByPropVal(myArray, prop, val){
for (var i = 0, length = myArray.length; i < length; i++) {
if (myArray[i][prop] == val){
return myArray[i];
}
}
}
var result = jsObjects.filter(x=> x.b === 6);
will be better, using return in filter sometimes you can't get result (I dunno why)
To get first object from array of objects by a specific property value:
function getObjectFromObjectsArrayByPropertyValue(objectsArray, propertyName, propertyValue) {
return objectsArray.find(function (objectsArrayElement) {
return objectsArrayElement[propertyName] == propertyValue;
});
}
function findObject () {
var arrayOfObjectsString = document.getElementById("arrayOfObjects").value,
arrayOfObjects,
propertyName = document.getElementById("propertyName").value,
propertyValue = document.getElementById("propertyValue").value,
preview = document.getElementById("preview"),
searchingObject;
arrayOfObjects = JSON.parse(arrayOfObjectsString);
console.debug(arrayOfObjects);
if(arrayOfObjects && propertyName && propertyValue) {
searchingObject = getObjectFromObjectsArrayByPropertyValue(arrayOfObjects, propertyName, propertyValue);
if(searchingObject) {
preview.innerHTML = JSON.stringify(searchingObject, false, 2);
} else {
preview.innerHTML = "there is no object with property " + propertyName + " = " + propertyValue + " in your array of objects";
}
}
}
pre {
padding: 5px;
border-radius: 4px;
background: #f3f2f2;
}
textarea, button {
width: 100%
}
<fieldset>
<legend>Input Data:</legend>
<label>Put here your array of objects</label>
<textarea rows="7" id="arrayOfObjects">
[
{"a": 1, "b": 2},
{"a": 3, "b": 4},
{"a": 5, "b": 6},
{"a": 7, "b": 8, "c": 157}
]
</textarea>
<hr>
<label>property name: </label> <input type="text" id="propertyName" value="b"/>
<label>property value: </label> <input type="text" id="propertyValue" value=6 />
</fieldset>
<hr>
<button onclick="findObject()">find object in array!</button>
<hr>
<fieldset>
<legend>Searching Result:</legend>
<pre id="preview">click find</pre>
</fieldset>
Using find with bind to pass specific key values to a callback function.
function byValue(o) {
return o.a === this.a && o.b === this.b;
};
var result = jsObjects.find(byValue.bind({ a: 5, b: 6 }));
var jsObjects = [{a: 1, b: 2}, {a: 3, b: 4}, {a: 5, b: 6}, {a: 7, b: 8}];
to access the third object, use: jsObjects[2];
to access the third object b value, use: jsObjects[2].b;
I have an object like:
Object {v: 1, b: 1, n: 1, m: 1, c: 2, d: 3}
I am trying to collect keys that has same values and generate an array (so in this case [v, b, n, m].
So if I know 1, how can I get v,b,n,m in an array?
You can use Object.keys() to get key values of the object, then filter values based on your condition using filter()
var obj = {
v: 1,
b: 1,
n: 1,
m: 1,
c: 2,
d: 3
},
val = 1;
var res = Object.keys(obj).filter(function(v) {
return obj[v] == val;
});
document.write('<pre>' + JSON.stringify(res, null, 4) + '</pre>');
Performance? Simple for...in loop.
var myObj = {v: 1, b: 1, n: 1, m: 1, c: 2, d: 3};
function collect (obj, value) {
var arr = [];
for (var key in obj)
if (obj.hasOwnProperty(key) && obj[key] === value)
arr.push(key);
return arr;
}
console.log(collect(myObj, 1));
Fancy? Object.keys, and Array.prototype.filter.
var myObj = {v: 1, b: 1, n: 1, m: 1, c: 2, d: 3};
function collect (obj, value) {
return Object.keys(obj).filter(key => obj[key] === value);
}
console.log(collect(myObj, 1));
using the underscore.js library you can do the following
var object = {v: 1, b: 1, n: 1, m: 1, c: 2, d: 3};
var output = _.map(object, function(value, key){
if(value == 1){
return key
}
}).filter(function(value){
return value;
});
console.log(output);