Lodash: Loop through array of objects and compare with key/value - lodash

I am looping through an array of objects and checking to see if the id in each object is contained in an object of key/value pairs. If the id is contained in the key value pairs, then I am assigning the value as a new object property.
So let's say I have an array of objects:
var arrayOfObjects = [
{
id: 1,
name: "bob"
},
{
id: 2,
name: "sue"
}
];
And I also have an object of key value pairs:
var keyValuePairs = { 1: "admin", 2: "user" }
I want to loop through my arrayOfObjects, and see if the id is in my keyValuePairs. If so, I want to add a new property to my arrayOfObjects to make it look like this:
var arrayOfObjects = [
{
id: 1,
name: "bob",
title: "admin"
},
{
id: 2,
name: "sue",
title: "user"
}
];
I've tried this, but it is not adding the 'title' property to my arrayOfObjects. Any thoughts on how I can do this using lodash?
return _.map(arrayOfObjects, function(obj) {
if(obj.id in keyValuePairs)
{
obj.title = keyValuePairs[obj.id];
}
return obj;
});


You can that easily without lodash or with the lodash equivalent, by iterating the array with Array#map, and if a value exists in keyValuePairs, assign the object, and the title to a new object:
var arrayOfObjects = [{"id":1,"name":"bob"},{"id":2,"name":"sue"},{"id":3,"name":"dave"}];
var keyValuePairs = { 1: "admin", 2: "user" }
var result = arrayOfObjects.map(function(o) {
return keyValuePairs[o.id] ? Object.assign({}, o, { title: keyValuePairs[o.id] }) : o;
});
console.log(result);

Related

Dynamic data assignment doesn't work on Vue js [duplicate]

In JavaScript, I've created an object like so:
var data = {
'PropertyA': 1,
'PropertyB': 2,
'PropertyC': 3
};
Is it possible to add further properties to this object after its initial creation if the properties name is not determined until run time? i.e.
var propName = 'Property' + someUserInput
//imagine someUserInput was 'Z', how can I now add a 'PropertyZ' property to
//my object?

Yes.
var data = {
'PropertyA': 1,
'PropertyB': 2,
'PropertyC': 3
};
data["PropertyD"] = 4;
// dialog box with 4 in it
alert(data.PropertyD);
alert(data["PropertyD"]);

ES6 for the win!
const b = 'B';
const c = 'C';
const data = {
a: true,
[b]: true, // dynamic property
[`interpolated-${c}`]: true, // dynamic property + interpolation
[`${b}-${c}`]: true
}
If you log data you get this:
{
a: true,
B: true,
interpolated-C: true,
B-C: true
}
This makes use of the new Computed Property syntax and Template Literals.

Yes it is possible. Assuming:
var data = {
'PropertyA': 1,
'PropertyB': 2,
'PropertyC': 3
};
var propertyName = "someProperty";
var propertyValue = "someValue";
Either:
data[propertyName] = propertyValue;
or
eval("data." + propertyName + " = '" + propertyValue + "'");
The first method is preferred. eval() has the obvious security concerns if you're using values supplied by the user so don't use it if you can avoid it but it's worth knowing it exists and what it can do.
You can reference this with:
alert(data.someProperty);
or
data(data["someProperty"]);
or
alert(data[propertyName]);

ES6 introduces computed property names, which allows you to do
let a = 'key'
let myObj = {[a]: 10};
// output will be {key:10}

I know that the question is answered perfectly, but I also found another way to add new properties and wanted to share it with you:
You can use the function Object.defineProperty()
Found on Mozilla Developer Network
Example:
var o = {}; // Creates a new object
// Example of an object property added with defineProperty with a data property descriptor
Object.defineProperty(o, "a", {value : 37,
writable : true,
enumerable : true,
configurable : true});
// 'a' property exists in the o object and its value is 37
// Example of an object property added with defineProperty with an accessor property descriptor
var bValue;
Object.defineProperty(o, "b", {get : function(){ return bValue; },
set : function(newValue){ bValue = newValue; },
enumerable : true,
configurable : true});
o.b = 38;
// 'b' property exists in the o object and its value is 38
// The value of o.b is now always identical to bValue, unless o.b is redefined
// You cannot try to mix both :
Object.defineProperty(o, "conflict", { value: 0x9f91102,
get: function() { return 0xdeadbeef; } });
// throws a TypeError: value appears only in data descriptors, get appears only in accessor descriptors

Here, using your notation:
var data = {
'PropertyA': 1,
'PropertyB': 2,
'PropertyC': 3
};
var propName = 'Property' + someUserInput
//imagine someUserInput was 'Z', how can I now add a 'PropertyZ' property to
//my object?
data[propName] = 'Some New Property value'

You can add as many more properties as you like simply by using the dot notation:
var data = {
var1:'somevalue'
}
data.newAttribute = 'newvalue'
or:
data[newattribute] = somevalue
for dynamic keys.

in addition to all the previous answers, and in case you're wondering how we're going to write dynamic property names in the Future using Computed Property Names ( ECMAScript 6 ), here's how:
var person = "John Doe";
var personId = "person_" + new Date().getTime();
var personIndex = {
[ personId ]: person
// ^ computed property name
};
personIndex[ personId ]; // "John Doe"
reference: Understanding ECMAScript 6 - Nickolas Zakas

Just an addition to abeing's answer above. You can define a function to encapsulate the complexity of defineProperty as mentioned below.
var defineProp = function ( obj, key, value ){
var config = {
value: value,
writable: true,
enumerable: true,
configurable: true
};
Object.defineProperty( obj, key, config );
};
//Call the method to add properties to any object
defineProp( data, "PropertyA", 1 );
defineProp( data, "PropertyB", 2 );
defineProp( data, "PropertyC", 3 );
reference: http://addyosmani.com/resources/essentialjsdesignpatterns/book/#constructorpatternjavascript

I know there are several answers to this post already, but I haven't seen one wherein there are multiple properties and they are within an array. And this solution by the way is for ES6.
For illustration, let's say we have an array named person with objects inside:
let Person = [{id:1, Name: "John"}, {id:2, Name: "Susan"}, {id:3, Name: "Jet"}]
So, you can add a property with corresponding value. Let's say we want to add a Language with a default value of EN.
Person.map((obj)=>({...obj,['Language']:"EN"}))
The Person array now would become like this:
Person = [{id:1, Name: "John", Language:"EN"},
{id:2, Name: "Susan", Language:"EN"}, {id:3, Name: "Jet", Language:"EN"}]

It can be useful if mixed new property add in runtime:
data = { ...data, newPropery: value}
However, spread operator use shallow copy but here we assign data to itself so should lose nothing

You can add properties dynamically using some of the options below:
In you example:
var data = {
'PropertyA': 1,
'PropertyB': 2,
'PropertyC': 3
};
You can define a property with a dynamic value in the next two ways:
data.key = value;
or
data['key'] = value;
Even more..if your key is also dynamic you can define using the Object class with:
Object.defineProperty(data, key, withValue(value));
where data is your object, key is the variable to store the key name and value is the variable to store the value.
I hope this helps!

I was looking for a solution where I can use dynamic key-names inside the object declaration (without using ES6 features like ... or [key]: value)
Here's what I came up with:
var obj = (obj = {}, obj[field] = 123, obj)
It looks a little bit complex at first, but it's really simple. We use the Comma Operator to run three commands in a row:
obj = {}: creates a new object and assigns it to the variable obj
obj[field] = 123: adds a computed property name to obj
obj: use the obj variable as the result of the parentheses/comma list
This syntax can be used inside a function parameter without the requirement to explictely declare the obj variable:
// The test function to see the result.
function showObject(obj) {
console.log(obj);
}
// My dynamic field name.
var field = "myDynamicField";
// Call the function with our dynamic object.
showObject( (obj = {}, obj[field] = 123, obj) );
/*
Output:
{
"myDynamicField": true
}
*/
Some variations
"strict mode" workaround:
The above code does not work in strict mode because the variable "obj" is not declared.
// This gives the same result, but declares the global variable `this.obj`!
showObject( (this.obj = {}, obj[field] = 123, obj) );
ES2015 code using computed property names in initializer:
// Works in most browsers, same result as the other functions.
showObject( {[field] = 123} );
This solution works in all modern browsers (but not in IE, if I need to mention that)
Super hacky way using JSON.parse():
// Create a JSON string that is parsed instantly. Not recommended in most cases.
showObject( JSON.parse( '{"' + field +'":123}') );
// read: showObject( JSON.parse( '{"myDynamicfield":123}') );
Allows special characters in keys
Note that you can also use spaces and other special characters inside computed property names (and also in JSON.parse).
var field = 'my dynamic field :)';
showObject( {[field] = 123} );
// result: { "my dynamic field :)": 123 }
Those fields cannot be accessed using a dot (obj.my dynamic field :) is obviously syntactically invalid), but only via the bracket-notation, i.e., obj['my dynamic field :)'] returns 123

The simplest and most portable way is.
var varFieldName = "good";
var ob = {};
Object.defineProperty(ob, varFieldName , { value: "Fresh Value" });
Based on #abeing answer!

Be careful while adding a property to the existing object using .(dot) method.
(.dot) method of adding a property to the object should only be used if you know the 'key' beforehand otherwise use the [bracket] method.
Example:
var data = {
'Property1': 1
};
// Two methods of adding a new property [ key (Property4), value (4) ] to the
// existing object (data)
data['Property2'] = 2; // bracket method
data.Property3 = 3; // dot method
console.log(data); // { Property1: 1, Property2: 2, Property3: 3 }
// But if 'key' of a property is unknown and will be found / calculated
// dynamically then use only [bracket] method not a dot method
var key;
for(var i = 4; i < 6; ++i) {
key = 'Property' + i; // Key - dynamically calculated
data[key] = i; // CORRECT !!!!
}
console.log(data);
// { Property1: 1, Property2: 2, Property3: 3, Property4: 4, Property5: 5 }
for(var i = 6; i < 2000; ++i) {
key = 'Property' + i; // Key - dynamically calculated
data.key = i; // WRONG !!!!!
}
console.log(data);
// { Property1: 1, Property2: 2, Property3: 3,
// Property4: 4, Property5: 5, key: 1999 }
Note the problem in the end of console log -
'key: 1999' instead of Property6: 6, Property7: 7,.........,Property1999: 1999. So the best way of adding dynamically created property is the [bracket] method.

A nice way to access from dynamic string names that contain objects (for example object.subobject.property)
function ReadValue(varname)
{
var v=varname.split(".");
var o=window;
if(!v.length)
return undefined;
for(var i=0;i<v.length-1;i++)
o=o[v[i]];
return o[v[v.length-1]];
}
function AssignValue(varname,value)
{
var v=varname.split(".");
var o=window;
if(!v.length)
return;
for(var i=0;i<v.length-1;i++)
o=o[v[i]];
o[v[v.length-1]]=value;
}
Example:
ReadValue("object.subobject.property");
WriteValue("object.subobject.property",5);
eval works for read value, but write value is a bit harder.
A more advanced version (Create subclasses if they dont exists, and allows objects instead of global variables)
function ReadValue(varname,o=window)
{
if(typeof(varname)==="undefined" || typeof(o)==="undefined" || o===null)
return undefined;
var v=varname.split(".");
if(!v.length)
return undefined;
for(var i=0;i<v.length-1;i++)
{
if(o[v[i]]===null || typeof(o[v[i]])==="undefined")
o[v[i]]={};
o=o[v[i]];
}
if(typeof(o[v[v.length-1]])==="undefined")
return undefined;
else
return o[v[v.length-1]];
}
function AssignValue(varname,value,o=window)
{
if(typeof(varname)==="undefined" || typeof(o)==="undefined" || o===null)
return;
var v=varname.split(".");
if(!v.length)
return;
for(var i=0;i<v.length-1;i++)
{
if(o[v[i]]===null || typeof(o[v[i]])==="undefined")
o[v[i]]={};
o=o[v[i]];
}
o[v[v.length-1]]=value;
}
Example:
ReadValue("object.subobject.property",o);
WriteValue("object.subobject.property",5,o);
This is the same that o.object.subobject.property

Here's how I solved the problem.
var obj = {
};
var field = "someouter.someinner.someValue";
var value = 123;
function _addField( obj, field, value )
{
// split the field into tokens
var tokens = field.split( '.' );
// if there's more than one token, this field is an object
if( tokens.length > 1 )
{
var subObj = tokens[0];
// define the object
if( obj[ subObj ] !== undefined ) obj[ subObj ] = {};
// call addfield again on the embedded object
var firstDot = field.indexOf( '.' );
_addField( obj[ subObj ], field.substr( firstDot + 1 ), value );
}
else
{
// no embedded objects, just field assignment
obj[ field ] = value;
}
}
_addField( obj, field, value );
_addField(obj, 'simpleString', 'string');
console.log( JSON.stringify( obj, null, 2 ) );
Generates the following object:
{
"someouter": {
"someinner": {
"someValue": 123
}
},
"simpleString": "string"
}

Yes it is possible. I have achieved using below implementation. for that I am getting array in response which I want in an object as list of attributes.
response = {
"equityMonths": [
{
"id": 1,
"month": "JANUARY",
"isEligible": false
},
{
"id": 2,
"month": "FEBRUARY",
"isEligible": true
},
{
"id": 3,
"month": "MARCH",
"isEligible": false
},
{
"id": 4,
"month": "APRIL",
"isEligible": true
},
{
"id": 5,
"month": "MAY",
"isEligible": false
},
{
"id": 6,
"month": "JUNE",
"isEligible": true
},
{
"id": 7,
"month": "JULY",
"isEligible": true
},
{
"id": 8,
"month": "AUGUST",
"isEligible": false
},
{
"id": 9,
"month": "SEPTEMBER",
"isEligible": true
},
{
"id": 10,
"month": "OCTOBER",
"isEligible": false
},
{
"id": 11,
"month": "NOVEMBER",
"isEligible": true
},
{
"id": 12,
"month": "DECEMBER",
"isEligible": false
}
]
}
here, I want equityMonths as an object and Jan to Dec it's key and isEligible as value. for that we have to use Object class's defineProperty() method which allows to add dynamic property into objects.
code for adding property dynamically to the object.
let equityMonth = new Object();
response.equityMonths.forEach(element => {
Object.defineProperty(equityMonth, element['month'], {
value: element['isEligible'],
writable: true,
enumerable: true,
configurable: true
});
});
console.log("DATA : " + JSON.stringify(equityMonth));
in above code we have array of equityMonths which we have converted as property into the object.
output:
DATA : {"JANUARY":false,"FEBRUARY":true,"MARCH":false,"APRIL":true,"MAY":false,"JUNE":true,"JULY":true,"AUGUST":false,"SEPTEMBER":true,"OCTOBER":false,"NOVEMBER":true,"DECEMBER":false}

A perfect easy way
var data = {
'PropertyA': 1,
'PropertyB': 2,
'PropertyC': 3
};
var newProperty = 'getThisFromUser';
data[newProperty] = 4;
console.log(data);
If you want to apply it on an array of data (ES6/TS version)
const data = [
{ 'PropertyA': 1, 'PropertyB': 2, 'PropertyC': 3 },
{ 'PropertyA': 11, 'PropertyB': 22, 'PropertyC': 33 }
];
const newProperty = 'getThisFromUser';
data.map( (d) => d[newProperty] = 4 );
console.log(data);

Definitely. Think of it as a dictionary or associative array. You can add to it at any point.

Unable to copy an array to an array using vue.js

I have a multiple selectbox using vuetify select component. I'm getting array of selected items and I want to merge status as true of selected items like [ { "ward": 1, "status": true }, { "ward": 2, "status": true} ]
I'm trying to copy selected items of array to another array but couldn't succeed. In console, I got selectedFruits as below.
methods: {
save() {
console.log(this.selectedFruits);
debugger;
this.selectedIndex.push({ ward: this.selectedFruits, status: true });
console.log(this.list);
},

You can try this
save(){
this.list = []
this.selectedFruits.forEach(e => {
this.list.push({ ward: e, status: true });
});
console.log(this.list)
}

If you want to copy an array or object without passing it by reference, do it like this
const newArray = JSON.parse(JSON.stringify(oldArray));

You can use the Spread-Operator for this.
Here an example:
const existingArr = [{ hi: 'foobar' }];
const arr = [{ a: 'foo', b: 'bar'}, { a: 'hello', b: 'world'}]
const newArr = [...existingArr, ...arr]
console.log(newArr)

Vue.js with iView Table - accessing Elasticsearch search response object

I am using the iView UI kit table in my Vue.js application that consumes an Elasticsearch API with axios. My problem is that I just can't seem to get to access the nested search response object, which is an array list object. I only get to access the 1st level fields, but not the nested ones. I don't know how to set the table row key in the iView table.
This is how my axios call and mapper methods look like:
listObjects(pageNumber){
const self = this
self.$Loading.start()
self.axios.get("/api/elasticsearch/")
.then(response => {
self.ajaxTableData = self.mapObjectToArray(response.data);
self.dataCount = self.ajaxTableData.length;
if(self.ajaxTableData.length < self.pageSize){
self.tableData = self.ajaxTableData;
} else {
self.tableData = self.ajaxTableData.slice(0,self.pageSize);
}
self.$Loading.finish()
})
.catch(e => {
self.tableData = []
self.$Loading.error()
self.errors.push(e)
})
},
mapObjectToArray(data){
var mappedData = Object.keys(data).map(key => {
return data[key];
})
return mappedData
},
The iView table columns look like this:
tableColumns: [
{
title: 'Study Date',
key: 'patientStudy.studyDate',
width: 140,
sortable: true,
sortType: 'desc'
},
{
title: 'Modality',
key: "generalSeries.modality",
width: 140,
sortable: true
},
...
]
The (raw) Elasticsearch documents look like this:
[
{ "score":1, "id":"3a710fa2c1b3f6125fc168c9308531b59e21d6b3",
"type":"dicom", "nestedIdentity":null, "version":-1, "fields":{
"highlightFields":{
},
"sortValues":[
],
"matchedQueries":[
],
"explanation":null,
"shard":null,
"index":"dicomdata",
"clusterAlias":null,
"sourceAsMap":{
"generalSeries":[
{
"seriesInstanceUid":"999.999.2.19960619.163000.1",
"modality":"MR",
"studyInstanceUid":"999.999.2.19960619.163000",
"seriesNumber":"1"
}
],
"patientStudy":[
{
"studyDate":"19990608"
}
]
}
}
]
And this is how the consumed object looks like:
As you can see, the fields I need to access are within the "sourceAsMap" object, and then nested in arrays.
How can I provide the iView table cell key to access them?
UPDATE:
I now "remapped" my Elasticsearch object before displaying it in the Vue.js table, and it works now. However, I don't think that the way I did it is very elegant or clean....maybe you can help me to do it in a better way. This is my method to remap the object:
getData(data){
let jsonMapped = []
for(let i = 0; i < data.length; i++){
let id = {}
id['id'] = data[i].id
let generalData = data[i]['sourceAsMap']['generalData'][0]
let generalSeries = data[i]['sourceAsMap']['generalSeries'][0]
let generalImage = data[i]['sourceAsMap']['generalImage'][0]
let generalEquipment = data[i]['sourceAsMap']['generalEquipment'][0]
let patient = data[i]['sourceAsMap']['patient'][0]
let patientStudy = data[i]['sourceAsMap']['patientStudy'][0]
let contrastBolus = data[i]['sourceAsMap']['contrastBolus'][0]
let specimen = data[i]['sourceAsMap']['specimen'][0]
jsonMapped[i] = Object.assign({}, id, generalData, generalSeries, generalImage, generalEquipment, patient,
patientStudy, contrastBolus, specimen)
}
return jsonMapped
},
The result is this:
Even though it now works, but how can I optimize this code?

A few functions can help you with your situation
let data = [{
key1: ['k1'],
key2: ['k2'],
key3: [{
subKey1: 'sk1',
subKey2: ['sk2'],
subObject: [{ name: 'John', surname: 'Doe' }],
items: [1, 2, 3, 5, 7]
}]
}];
function mapIt(data) {
if (isSingletonArray(data)) {
data = data[0];
}
for(const key in data) {
if (isSingletonArray(data[key])) {
data[key] = mapIt(data[key][0]);
} else {
data[key] = data[key];
}
}
return data;
}
function isSingletonArray(obj) {
return typeof obj === 'object' && Array.isArray(obj) && obj.length === 1;
}
console.log(mapIt(data));
Outputs:
{
key1: 'k1',
key2: 'k2',
key3: {
subKey1: 'sk1',
subKey2: 'sk2',
subObject: { name: 'John', surname: 'Doe' },
items: [ 1, 2, 3, 5, 7 ]
}
}
You can check it in your browser. mapIt unwraps the singleton arrays into objects or primitives.
But I recommend you to watch out special elastic client libraries for javascript. It could save you from writing extra code.

Filter data using lodash

How can filter the data with some inner attribute value.
updated_id='1234';
var result= _.map(self.list, function (item) {
// return only item.User_Info.id=updated_id
});

You can use the lodash#matchesProperty variant of lodash#filter to filter out objects that you need using the path of the property. The variant is in the 3rd example of the lodash#filter documentation.
var result = _.filter(self.list, ['User_Info.id', updated_id]);
var self = {
list: [
{ User_Info: { id: '4321' } },
{ User_Info: { id: '4321' } },
{ User_Info: { id: '1234' } },
{ User_Info: { id: '3214' } },
{ User_Info: { id: '2143' } }
]
};
var updated_id = '1234';
var result = _.filter(self.list, ['User_Info.id', updated_id]);
console.log(result);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

lodash has a filter method:
const updated_id='1234';
const result= _.filter(self.list, item => item.User_Info.id === updated_id);

Use lodash _.filter method:
_.filter(collection, [predicate=_.identity])
Iterates over elements of collection, returning an array of all elements predicate returns truthy for. The predicate is invoked with three arguments: (value, index|key, collection).
with predicate as custom function
_.filter(myArr, function(o) {
return o.name == 'john';
});
with predicate as part of filtered object (the _.matches iteratee shorthand)
_.filter(myArr, {name: 'john'});
with predicate as [key, value] array (the _.matchesProperty iteratee shorthand.)
_.filter(myArr, ['name', 'John']);

How to chain get and map the result with lodash?

I've got a list I'm trying to pull an object from using _.get but following that selection I need to loop over the object to create a new property. So far I've been successful using a combination of _.get and _.map as shown below but I'm hoping I can use _.chain in some way.
var selected = _.get(results, selectedId);
return _.map([selected], result => {
var reviews = result.reviews.map(review => {
var reviewed = review.userId === authenticatedUserId;
return _.extend({}, review, {reviewed: reviewed});
});
return _.extend({}, result, {reviews: reviews});
})[0];
Is it possible to do a transform like this using something other than map (as map required me to break this up/ creating an array with a solo item inside it). Thank you in advance!

I can see that you're creating unnecessary map() calls, you can simply reduce all those work into something like this:
var output = {
reviews: _.map(results[selectedId], function(review) {
return _.defaults({
reviewed: review.userId === authenticatedUserId
}, review);
})
};
The defaults() method is similar to extend() except once a property is set, additional values of the same property are ignored.
var selectedId = 1;
var authenticatedUserId = 1;
var results = {
1: [
{ userId: 1, text: 'hello' },
{ userId: 2, text: 'hey' },
{ userId: 1, text: 'world?' },
{ userId: 2, text: 'nah' },
]
};
var output = {
reviews: _.map(results[selectedId], function(review) {
return _.defaults({
reviewed: review.userId === authenticatedUserId
}, review);
})
};
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