Develop Reference

FInd duplicates withtin array based on certain keys using lodash?

I have an array like this
let data = [{x:1,y:2,z:3},{x:1,y:2,z:3},{x:1,y:2,z:4},{x:11,y:2,z:3}]
Now I want to get only those items whose x,y,z values are the same.so expected output should be
{x:1,y:2,z:3}
Because {x:1,y:2,z:3} has duplicate values but rest of them not so I don't want to get rest of them because they do not have any duplicates. Please tell me how can I achieve this?

For lodash 4.17.15,
You can first use _.uniqWith and _.isEqual to find the unique values.
_.uniqWith(data, _.isEqual); // [{x:1,y:2,z:3},{x:1,y:2,z:4},{x:11,y:2,z:3}]
Then use _.difference to remove the unique values from the array, leaving just the duplicates
_.difference(data, _.uniqWith(data, _.isEqual)); // [{x:1,y:2,z:3}]

let data = [{x:1,y:2,z:3},{x:1,y:2,z:3},{x:1,y:2,z:4},{x:11,y:2,z:3},{x:11,y:2,z:3}]
function filterDuplicates(data) {
let dic = {};
data.forEach(obj => {
let strObj = JSON.stringify(obj, Object.keys(obj).sort());
if(strObj in dic) {
++dic[strObj];
return;
}
dic[strObj] = 0;
})
return Object.entries(dic).filter(([key, value]) => value > 0).map(([el]) => JSON.parse(el));
}
console.log(filterDuplicates(data));

Build an object to track the duplicates and use Object.values and filter
let data = [
{ x: 1, y: 2, z: 3 },
{ x: 1, y: 2, z: 3 },
{ x: 1, y: 2, z: 4 },
{ x: 11, y: 2, z: 3 },
];
const all = {};
data.forEach(({ x, y, z }) => {
const key = `x${x}y${y}z${z}`;
all[key] = key in all ? { x, y, z } : null;
});
const res = Object.values(all).filter(Boolean);
console.log(res);

How to insert a object in an array (as a element )

I am from C++ background.
I am trying to translate a C++ code to JavaScript.
in C++ we have vector < pair < int,int > > to store pairs.
in JS i have a situation. i want to store 2D coordinates. i actually want to push new coordinates to the array.
i did like
first I created a Object
const coordinate = {
x= 9,
y= 10
}
Then i tried to push that object into the array CoordinateStorage that i want this object to get stored
CoordinatesStorage.unshift({X : coordinate.x, Y : coordinates.y});
I know this code shown above is absolutely wrong to store an object into the array. I searched out for sources but i got nothing useful.
Please recommend some sources that i can refer for such translation related problems if possible.

Generally speaking, we should use the .push method for an array.
There are other methods available you can find them here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array but the .push method for your case is more suitable.
Basically, as a result, we want to have something like this:
[ {x: 2, y: 4 }, { x: 2, y: 4 } ] We have an array of objects.
Or we could also have an array of arrays:
[[1, 2], [3, 4], [4, 6]] Not sure if it okay for your case, but maybe as an option.
Also, we could create a class Vector and we might have something like
[ Vector { x: 1, y: 2 }, Vector { x: 3, y: 4 }, Vector { x: 4, y: 6 } ]
Let's take a look at the examples:
Using the plain object for the vector:
const coordinate1 = {
x: 2,
y: 4
};
const coordinate2 = {
x: 3,
y: 4
};
const coordinatesStorage = [];
coordinatesStorage.push(coordinate1);
coordinatesStorage.push(coordinate2);
If you will do console.log(coordinatesStorage) you will see [ { x: 2, y: 4 }, { x: 3, y: 4 } ]
Using the array to store a vector:
const coordinate1 = [1, 2];
const coordinate2 = [3, 4];
const coordinatesStorage = [];
coordinatesStorage.push(coordinate1);
coordinatesStorage.push(coordinate2);
The coordinatesStorage will be [ [ 1, 2 ], [ 3, 4 ] ]
Using the Vector class:
Maybe in your case, it would be more helpful to operate with a class Vector:
class Vector {
constructor(x, y) {
this.x = x;
this.y = y;
}
}
const coordinatesStorage = [];
coordinatesStorage.push(new Vector(1, 2));
coordinatesStorage.push(new Vector(3, 4));
coordinatesStorage.push(new Vector(4, 6));
And here in the console you will see [ Vector { x: 1, y: 2 }, Vector { x: 3, y: 4}, Vector { x: 4, y: 6 } ]
Take a look at the Vector implementations in JS:
https://gist.github.com/jjgrainger/808640fcb5764cf92c3cad960682c677
https://github.com/maxkueng/victor/blob/master/index.js
I hope this helps. Good luck!

First initialize the array
var CoordinatesStorage = [];
//create object
const coordinate = {
x: 9, // Note - the operator is colon : not = as in the question
y: 10
}
// push to array
CoordinatesStorage.push(coordinate);
Now your array will be like this [{x:9, y:10}] if you push again the array will be [{x:9, y:10}, {x:9, y:10}]
Tip: Arrays are denoted by square brackets eg: ['math', 'science', 'english']
Objects are denoted by key-value pairs wrapped in curly brackets
eg: var student = {
name: "John", // string value
age: 6, // integer value
sex: "M",
phone: [123456789 , 564654654] // value is of array of 2 items
}

Javascript Map function does not preserve the original object

I have a scenario wherein i have
var data = [
{
"x": 1,
"y": 0.27,
"classifier": 1
},
{
"x": 2,
"y": 0.88,
"classifier": 1
}
]
I want another object data2 with y=1-y, which i obtain with:
var data2 = data.map(function(el) {el.y = 1-el.y; return el});
data2[0]
Object {x: 1, y: 0.73, classifier: 1}
data2[1]
Object {x: 2, y: 0.12, classifier: 1}
which is the correct form that i want the data in. However the issue is i want to preserve the original data as well. Right now even data has mutated data.
data[0]
Object {x: 1, y: 0.73, classifier: 1}
data[1]
Object {x: 2, y: 0.12, classifier: 1}
Is map the right function to use here? Am i using it correctly?

While creating a new array, you let its values point to the original objects, which you mutate by assigning to their object properties.
Instead you could also create (shallow) copies of the objects with Object.assign:
var data2 = data.map(function(el) {
return Object.assign({}, el, { y: 1-el.y });
});
Or with arrow function:
var data2 = data.map( el => Object.assign({}, el, { y: 1-el.y }) );
var data = [
{
"x": 1,
"y": 0.27,
"classifier": 1
},
{
"x": 2,
"y": 0.88,
"classifier": 1
}
]
var data2 = data.map( el => Object.assign({}, el, { y: 1-el.y }) );
console.log (data);

You're modifying the original element object, which isn't a full deep copy of the original data.
Create a copy of el in the function and then calculate the new .y. For example:
var data2 = data.map(function(el) {
return {
x : el.x,
y : 1-el.y,
classifier : el.classifier
};
});

Format json array to chart input

Hi i am getting json array as response of ajax request:
{"chart":{"2016-03-08":"1","2016-03-07":"4","2016-03-06":0,"2016-03-05"
:0,"2016-03-04":0,"2016-03-03":"145","2016-03-02":0}}
Now i want to prepare a chart by giving these values to chart input as below: ( i want output like this from above array )
data: [{
y: '2016-03-07',
a: 100
}, {
y: '2016-03-08',
a: 75
}, {
y: '2016-03-06',
a: 50
}, {
y: '2016-03-05',
a: 75
}, {
y: '2016-03-09',
a: 50
}, {
y: '2016-03-03',
a: 75
}, {
y: '2016-03-02',
a: 180
}
],
I have tried :
var chart_params = {};
for (var key in data_chart) {
let value = data_chart[key];
chart_params = '{ y:'+ key+ ', a: '+value+' }';
}
console.log(chart_params);
but it is not giving output as expected

Try this
data = {"chart":{"2016-03-08":"1","2016-03-07":"4","2016-03-06":0,"2016-03-05" :0,"2016-03-04":0,"2016-03-03":"145","2016-03-02":0}}
var chart_params = [];
data_chart = data.chart;
for (var key in data_chart) {
var value = data_chart[key];
chart_params.push({ y: key, a:value});
}
console.log(chart_params);
jsfiddle: https://jsfiddle.net/hb8qd1p8/1/

#madalin's answer is the correct fix for your issue, though another option to accomplish what you want is to use map:-
var data = {"chart":{"2016-03-08":"1","2016-03-07":"4","2016-03-06":0,"2016-03-05":0,"2016-03-04":0,"2016-03-03":"145","2016-03-02":0}};
var array = Object.keys(data.chart).map(function (key) {
return { y: key, a: data.chart[key] };
});
document.write(JSON.stringify(array, null, 4));

Convert Js Array to JSON object with keys

I want to use the same object for jQplot and a library built on jQtable.
jQplot is fine with arrays but jQtable's library needs an named object (dictionary).
vals =
[
[1, 2],
[3,5.12],
[5,13.1],
[7,33.6],
[9,85.9],
[12,54],
[11,219.9]
];
This is my js array
I want it to be like
{
data: [{
X: 1,
Y: 2
},
{
X: 3,
Y: 5.12
},
{
X: 5,
Y: 13.1
}]
}
How to convert js array into named JSON array of objects? Are there any built in methods or I define my own method to read up that array and create a String for JSON?

var array = vals.map(function(val) {
return {
X : val[0],
Y : val[1]
};
});

var data = Object.keys(vals).map(function(key) {
return {X : vals[key][0], Y : vals[key][1]};
});