Related
For instance, a variable named arrayElements of type array contains:
[{id:1, value:5},{id:2, value:6},{id:3, value:7},{id:4, value:8}].
How do I get the position of the array element with id === 3(3rd element) in the arrayElements variable besides using loop?
thanks.
You have to loop at one point. But you can abstract it to look like you're not looping
function indexOfCallback(arr, callback, startIndex) {
if (typeof startIndex == 'undefined') {
startIndex = 0;
}
for(var i=startIndex; i < arr.length; i ++) {
if (callback(arr[i])) {
return i;
}
}
return -1;
}
var array = [{id:1, value:5},{id:2, value:6},{id:3, value:7},{id:4, value:8}];
// Search on id === 3
console.log(indexOfCallback(array, function(obj){
return obj.id === 3;
}));
// Search on value === 6
console.log(indexOfCallback(array, function(obj){
return obj.value === 6;
}));
As mentioned by Anthony, this is proposed for ECMAScript 6. Here's the more complete polyfill https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findIndex
if (!Array.prototype.findIndex) {
Array.prototype.findIndex = function(predicate) {
if (this == null) {
throw new TypeError('Array.prototype.find called on null or undefined');
}
if (typeof predicate !== 'function') {
throw new TypeError('predicate must be a function');
}
var list = Object(this);
var length = list.length >>> 0;
var thisArg = arguments[1];
var value;
for (var i = 0; i < length; i++) {
value = list[i];
if (predicate.call(thisArg, value, i, list)) {
return i;
}
}
return -1;
};
}
console.log(array.findIndex(function(obj){
return obj.id === 3;
}));
arrayElements.map(o => o.id).indexOf(3);
Notes:
Possibly slower than a loop because transforms whole array prior to
search. But with high-level languages like Javascript, you never
know.
Infinitely more readable than a loop.
IE compatible (unlike findIndex as of 2017).
In an array like this, you cant access elements by id. So using a loop is the best solution you have. However, depending on your use case you could also consider using an object instead of an array for direct access.
var container = { 1: {id:1, value:5}, 2: {id:2, value:6}, 3: {id:3, value:7} }
const arrayElements = [
{ id: 1, value: 5 },
{ id: 2, value: 6 },
{ id: 3, value: 7 },
{ id: 4, value: 8 }
]
console.log(arrayElements.findIndex((item) => item.id === 3))
You can use an array filter but I think that you will get a better solution using a loop.
var array = [{id:1, value:5},{id:2, value:6},{id:3, value:7},{id:4, value:8}];
var result = array.filter(condition);
function condition(value, index){
if (value.id === 3) return index;
}
console.log(result);
I wrote a function for you that you can use get the job done, but it uses a loop:
var yourObjArray = [{id:1, value:5},{id:2, value:6},{id:3, value:7},{id:4, value:8}];
function objArrayIndex(objArray){
for(var i = 0; i < objArray.length; i++){
if(objArray[i]['id'] == 3){
return i;
}
}
return -1;
}
console.log(objArrayIndex(yourObjArray));
$.each(constructions, function(i,v) {
if ($.inArray(v.name, map[ii].buildings) == -1) {//stuff}
};
Where constructions is an array of objects, each with a unique name. map[ii].buildings is an array containing some of these objects. I want to iterate each object in constructions, checking if its name parameter appears in the objects of map[ii].buildings.
The above code works if the each element in the map[ii].buildings array is just the text string of the object name, but not if the element is the entire object.. close, but no dice >.<
Try using $.grep() instead of $.inArray(); you can specify a function to do the filtering for you.
Instead of checking for -1, you check whether the array that $.grep() returns has length == 0
Simple example: (would be easier if you posted the code / example of what "constructions" objects look like)
var constructions = [{
Name: "Mess hall",
SqFt: 5000
}, {
Name: "Infirmary",
SqFt: 2000
}, {
Name: "Bungalow",
SqFt: 2000
}, {
Name: "HQ",
SqFt: 2000
}];
var buildings = [{
Name: "Infirmary",
SqFt: 2000
}, {
Name: "HQ",
SqFt: 2000
}];
// found buildings will be list of items in "constructions" that is not in "buildings"
var foundBuildings = $.grep(constructions, function (constructionsItem) {
return $.grep(buildings, function (buildingsItem) {
return buildingsItem.Name === constructionsItem.Name
}).length == 0; // == 0 means "not in", and > 0 means "in"
});
// this just renders the results all pretty for ya
$.each(foundBuildings, function (idx, item) {
$("#output").append("<div>" + item.Name + "</div>");
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id='output'></div>
Example jsFiddle: http://jsfiddle.net/eLeuy9eg/3/
The non-jQuery way of doing this would be to use filter. Something like this:
// pass in an array and the key for which you want values
// it returns an array of those values
function getValues(arr, key) {
return arr.map(function (el) { return el[key]; });
}
function notFoundIn(arr, arr2) {
// grab the names of the buildings
var buildings = getValues(arr2, 'name');
// grab the names from the construction objects and filter
// those that are not in the building array
return getValues(arr, 'name').filter(function (el) {
return buildings.indexOf(el) === -1;
});
}
notFoundIn(constructions, buildings); // eg [ "one", "three" ]
DEMO
You could even add a new method to the array prototype. With this one you can use either simple arrays, or arrays of objects if you pass in a key. Note in this example I've replaced map and filter with loops that perform the same functions, but faster (see comments):
function getValues(arr, key) {
var out = [];
for (var i = 0, l = arr.length; i < l; i++) {
out.push(arr[i][key]);
}
return out;
}
if (!Array.prototype.notFoundIn) {
Array.prototype.notFoundIn = function (inThisArray, key) {
var thisArr = key ? getValues(this, key) : this;
var arrIn = key ? getValues(inThisArray, key) : inThisArray;
var out = [];
for (var i = 0, l = thisArr.length; i < l; i++) {
if (arrIn.indexOf(thisArr[i]) === -1) {
out.push(thisArr[i]);
}
}
return out;
}
}
constructions.notFoundIn(buildings, 'name');
[1, 2, 3].notFoundIn([2]); // [1, 3]
DEMO
I think the title explains it well enough. I've got an array that has two values per object and I need to look up the object by one of those values then assign a third to it.
Here are the guts:
$slides.push({
img: el.attr('href'),
desc: el.attr('title').split('Photo #')[1]
});
Which builds an array as such:
Object
desc: 127
img: img/aaron1.jpg
Object
desc: 128
img: img/aaron2.jpg
I'd like to look up the desc value, then assign a third value of in: yes
$slides.findInArray('desc', '127').addValueToObject('in','yes')
http://jsfiddle.net/S3cpa/
var test = [
{
desc: 127,
img: 'img/aaron1.jpg',
},
{
desc: 128,
img: 'img/aaron2.jpg',
}
];
function getObjWhenPropertyEquals(prop, val)
{
for (var i = 0, l = test.length; i < l; i++) {
// check the obj has the property before comparing it
if (typeof test[i][prop] === 'undefined') continue;
// if the obj property equals our test value, return the obj
if (test[i][prop] === val) return test[i];
}
// didn't find an object with the property
return false;
}
// look up the obj and save it
var obj = getObjWhenPropertyEquals('desc', 127);
// set the new property if obj was found
obj.in = obj && 'yes';
easy way
for (var i = 0; i < $slides.length; i++)
{
if ($slides[i]["desc"] == "TEST_VALUE")
{
$slides[i]['in']='yes';
}
}
Another way
Array.prototype.findInArray =function(propName,value)
{
var res={};
if(propName && value)
{
for (var i=0; i<this.length; i++)
{
if(this[i][propName]==value)
{
res = this[i];
break;
}
}
}
return res;
}
Object.prototype.addValueToObject =function(prop,value)
{
this[prop]=value;
}
---Using It--
$slides.findInArray('desc', '127').addValueToObject('in','yes');
http://jsfiddle.net/s6ThK/
You need to run it through a for loop
// Loop through the array
for (var i = 0 ; i < $slides.length ; i++)
{
// Compare current item to the value you're looking for
if ($slides[i]["desc"] == myValue)
{
//do what you gotta do
$slides[i]["desc"] = newValue;
break;
}
}
With modern JS it can be simply done:
var obj = $slides.find(e => e.desc === '127');
if (obj) {
obj.in = 'yes';
}
For example, I have:
var Data = [
{ id_list: 1, name: 'Nick', token: '312312' },
{ id_list: 2, name: 'John', token: '123123' },
]
Then, I want to sort/reverse this object by name, for example. And then I want to get something like this:
var Data = [
{ id_list: 2, name: 'John', token: '123123' },
{ id_list: 1, name: 'Nick', token: '312312' },
]
And now I want to know the index of the object with property name='John' to get the value of the property token.
How do I solve the problem?
Since the sort part is already answered. I'm just going to propose another elegant way to get the indexOf of a property in your array
Your example is:
var Data = [
{id_list:1, name:'Nick', token:'312312'},
{id_list:2, name:'John', token:'123123'}
]
You can do:
var index = Data.map(function(e) { return e.name; }).indexOf('Nick');
var Data = [{
id_list: 1,
name: 'Nick',
token: '312312'
},
{
id_list: 2,
name: 'John',
token: '123123'
}
]
var index = Data.map(function(e) {
return e.name;
}).indexOf('Nick');
console.log(index)
Array.prototype.map is not available on Internet Explorer 7 or Internet Explorer 8. ES5 Compatibility
And here it is with ES6 and arrow syntax, which is even simpler:
const index = Data.map(e => e.name).indexOf('Nick');
If you're fine with using ES6, arrays now have the findIndex function. Which means you can do something like this:
const index = Data.findIndex(item => item.name === 'John');
As the other answers suggest, looping through the array is probably the best way. But I would put it in its own function, and make it a little more abstract:
function findWithAttr(array, attr, value) {
for(var i = 0; i < array.length; i += 1) {
if(array[i][attr] === value) {
return i;
}
}
return -1;
}
var Data = [
{id_list: 2, name: 'John', token: '123123'},
{id_list: 1, name: 'Nick', token: '312312'}
];
With this, not only can you find which one contains 'John', but you can find which contains the token '312312':
findWithAttr(Data, 'name', 'John'); // returns 0
findWithAttr(Data, 'token', '312312'); // returns 1
findWithAttr(Data, 'id_list', '10'); // returns -1
The function returns -1 when not found, so it follows the same construct as Array.prototype.indexOf().
If you're having issues with Internet Explorer, you could use the map() function which is supported from 9.0 onward:
var index = Data.map(item => item.name).indexOf("Nick");
var index = Data.findIndex(item => item.name == "John")
Which is a simplified version of:
var index = Data.findIndex(function(item){ return item.name == "John"})
From mozilla.org:
The findIndex() method returns the index of the first element in the array that satisfies the provided testing function. Otherwise -1 is returned.
Only way known to me is to loop through all array:
var index = -1;
for(var i=0; i<Data.length; i++)
if(Data[i].name === "John") {
index = i;
break;
}
Or case insensitive:
var index = -1;
for(var i=0; i<Data.length; i++)
if(Data[i].name.toLowerCase() === "john") {
index = i;
break;
}
On result variable index contain index of object or -1 if not found.
A prototypical way
(function(){
if (!Array.prototype.indexOfPropertyValue){
Array.prototype.indexOfPropertyValue = function(prop, value){
for (var index = 0; index < this.length; index++){
if (this[index][prop]){
if (this[index][prop] == value){
return index;
}
}
}
return -1;
}
}
})();
// Usage:
var Data = [
{id_list:1, name:'Nick', token:'312312'}, {id_list:2, name:'John', token:'123123'}];
Data.indexOfPropertyValue('name', 'John'); // Returns 1 (index of array);
Data.indexOfPropertyValue('name', 'Invalid name') // Returns -1 (no result);
var indexOfArray = Data.indexOfPropertyValue('name', 'John');
Data[indexOfArray] // Returns the desired object.
you can use filter method
const filteredData = data.filter(e => e.name !== 'john');
Just go through your array and find the position:
var i = 0;
for(var item in Data) {
if(Data[item].name == 'John')
break;
i++;
}
alert(i);
let indexOf = -1;
let theProperty = "value"
let searchFor = "something";
theArray.every(function (element, index) {
if (element[theProperty] === searchFor) {
indexOf = index;
return false;
}
return true;
});
collection.findIndex(item => item.value === 'smth') !== -1
You can use Array.sort using a custom function as a parameter to define your sorting mechanism.
In your example, it would give:
var Data = [
{id_list:1, name:'Nick',token:'312312'},{id_list:2,name:'John',token:'123123'}
]
Data.sort(function(a, b){
return a.name < b.name ? -1 : a.name > b.name ? 1 : 0;
});
alert("First name is : " + Data[0].name); // alerts 'John'
alert("Second name is : " + Data[1].name); // alerts 'Nick'
The sort function must return either -1 if a should come before b, 1 if a should come after b and 0 if both are equal. It's up to you to define the right logic in your sorting function to sort the array.
Missed the last part of your question where you want to know the index. You would have to loop through the array to find that as others have said.
This might be useful:
function showProps(obj, objName) {
var result = "";
for (var i in obj)
result += objName + "." + i + " = " + obj[i] + "\n";
return result;
}
I copied this from Working with objects.
Use a small workaround:
Create a new array with names as indexes. After that all searches will use indexes. So, only one loop. After that you don't need to loop through all elements!
var Data = [
{id_list:1, name:'Nick',token:'312312'},{id_list:2,name:'John',token:'123123'}
]
var searchArr = []
Data.forEach(function(one){
searchArr[one.name]=one;
})
console.log(searchArr['Nick'])
http://jsbin.com/xibala/1/edit
Live example.
I extended Chris Pickett's answer, because in my case I needed to search deeper than one attribute level:
function findWithAttr(array, attr, value) {
if (attr.indexOf('.') >= 0) {
var split = attr.split('.');
var attr1 = split[0];
var attr2 = split[1];
for(var i = 0; i < array.length; i += 1) {
if(array[i][attr1][attr2] === value) {
return i;
}
}
} else {
for(var i = 0; i < array.length; i += 1) {
if(array[i][attr] === value) {
return i;
}
}
};
};
You can pass 'attr1.attr2' into the function.
Use this:
Data.indexOf(_.find(Data, function(element) {
return element.name === 'John';
}));
It is assuming you are using Lodash or Underscore.js.
var fields = {
teste:
{
Acess:
{
Edit: true,
View: false
}
},
teste1:
{
Acess:
{
Edit: false,
View: false
}
}
};
console.log(find(fields,'teste'));
function find(fields,field) {
for(key in fields) {
if(key == field) {
return true;
}
}
return false;
}
If you have one Object with multiple objects inside, if you want know if some object are include on Master object, just use find(MasterObject, 'Object to Search'). This function will return the response if it exists or not (TRUE or FALSE). I hope to help with this - can see the example on JSFiddle.
If you want to get the value of the property token then you can also try this:
let data=[
{ id_list: 1, name: 'Nick', token: '312312' },
{ id_list: 2, name: 'John', token: '123123' },
]
let resultingToken = data[_.findKey(data,['name','John'])].token
where _.findKey is a Lodash function.
You can use findIndex in Lodash library.
Example:
var users = [
{ 'user': 'barney', 'active': false },
{ 'user': 'fred', 'active': false },
{ 'user': 'pebbles', 'active': true }
];
_.findIndex(users, function(o) { return o.user == 'barney'; });
// => 0
// The `_.matches` iteratee shorthand.
_.findIndex(users, { 'user': 'fred', 'active': false });
// => 1
// The `_.matchesProperty` iteratee shorthand.
_.findIndex(users, ['active', false]);
// => 0
// The `_.property` iteratee shorthand.
_.findIndex(users, 'active');
// => 2
Alternatively to German Attanasio Ruiz's answer, you can eliminate the second loop by using Array.reduce() instead of Array.map();
var Data = [
{ name: 'hypno7oad' }
]
var indexOfTarget = Data.reduce(function (indexOfTarget, element, currentIndex) {
return (element.name === 'hypno7oad') ? currentIndex : indexOfTarget;
}, -1);
Maybe the Object.keys, Object.entries, and Object.values methods might help.
Using Underscore.js:
var index = _.indexOf(_.pluck(item , 'name'), 'Nick');
I have the following array
var countries = {};
countries.results = [
{id:'AF',name:'Afghanistan'},
{id:'AL',name:'Albania'},
{id:'DZ',name:'Algeria'}
];
How can I remove an item from this array using its name or id ?
Thank you
Created a handy function for this..
function findAndRemove(array, property, value) {
array.forEach(function(result, index) {
if(result[property] === value) {
//Remove from array
array.splice(index, 1);
}
});
}
//Checks countries.result for an object with a property of 'id' whose value is 'AF'
//Then removes it ;p
findAndRemove(countries.results, 'id', 'AF');
Array.prototype.removeValue = function(name, value){
var array = $.map(this, function(v,i){
return v[name] === value ? null : v;
});
this.length = 0; //clear original array
this.push.apply(this, array); //push all elements except the one we want to delete
}
countries.results.removeValue('name', 'Albania');
Try this:
var COUNTRY_ID = 'AL';
countries.results =
countries.results.filter(function(el){ return el.id != COUNTRY_ID; });
Try this.(IE8+)
//Define function
function removeJsonAttrs(json,attrs){
return JSON.parse(JSON.stringify(json,function(k,v){
return attrs.indexOf(k)!==-1 ? undefined: v;
}));}
//use object
var countries = {};
countries.results = [
{id:'AF',name:'Afghanistan'},
{id:'AL',name:'Albania'},
{id:'DZ',name:'Algeria'}
];
countries = removeJsonAttrs(countries,["name"]);
//use array
var arr = [
{id:'AF',name:'Afghanistan'},
{id:'AL',name:'Albania'},
{id:'DZ',name:'Algeria'}
];
arr = removeJsonAttrs(arr,["name"]);
You can delete by 1 or more properties:
//Delets an json object from array by given object properties.
//Exp. someJasonCollection.deleteWhereMatches({ l: 1039, v: '3' }); ->
//removes all items with property l=1039 and property v='3'.
Array.prototype.deleteWhereMatches = function (matchObj) {
var indexes = this.findIndexes(matchObj).sort(function (a, b) { return b > a; });
var deleted = 0;
for (var i = 0, count = indexes.length; i < count; i++) {
this.splice(indexes[i], 1);
deleted++;
}
return deleted;
}
you can use delete operator to delete property by it's name
delete objectExpression.property
or iterate through the object and find the value you need and delete it:
for(prop in Obj){
if(Obj.hasOwnProperty(prop)){
if(Obj[prop] === 'myValue'){
delete Obj[prop];
}
}
}
This that only requires javascript and appears a little more readable than other answers.
(I assume when you write 'value' you mean 'id')
//your code
var countries = {};
countries.results = [
{id:'AF',name:'Afghanistan'},
{id:'AL',name:'Albania'},
{id:'DZ',name:'Algeria'}
];
// solution:
//function to remove a value from the json array
function removeItem(obj, prop, val) {
var c, found=false;
for(c in obj) {
if(obj[c][prop] == val) {
found=true;
break;
}
}
if(found){
delete obj[c];
}
}
//example: call the 'remove' function to remove an item by id.
removeItem(countries.results,'id','AF');
//example2: call the 'remove' function to remove an item by name.
removeItem(countries.results,'name','Albania');
// print our result to console to check it works !
for(c in countries.results) {
console.log(countries.results[c].id);
}
it worked for me..
countries.results= $.grep(countries.results, function (e) {
if(e.id!= currentID) {
return true;
}
});
You can do it with _.pullAllBy.
var countries = {};
countries.results = [
{id:'AF',name:'Afghanistan'},
{id:'AL',name:'Albania'},
{id:'DZ',name:'Algeria'}
];
// Remove element by id
_.pullAllBy(countries.results , [{ 'id': 'AL' }], 'id');
// Remove element by name
// _.pullAllBy(countries.results , [{ 'name': 'Albania' }], 'name');
console.log(countries);
.as-console-wrapper {
max-height: 100% !important;
top: 0;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.min.js"></script>
Maybe this is helpful, too.
for (var i = countries.length - 1; i--;) {
if (countries[i]['id'] === 'AF' || countries[i]['name'] === 'Algeria'{
countries.splice(i, 1);
}
}
The accepted answer is problematic as it attaches a function to the Array prototype. That function will show up whenever you run thru the array using a for loop:
for (var key in yourArray) {
console.log(yourArray[key]);
}
One of the values that will show up will be the function. The only acceptable way to extend base prototypes (although it is generally discouraged as it pollutes the global space) is to use the .defineProperty method:
Object.defineProperty(Object.prototype, "removeValue", {
value: function (val) {
for (var i = 0; i < this.length; i++) {
if (this[i] === val) {
this.splice(i, 1);
i--;
}
}
return this;
},
writable: true,
configurable: true,
enumerable: false
});