I have array, created from json:
var array = [{"name":"name1","group":"group1","id":"123", ...},
{"name":"name2","group":"group2","id":"456", ...},
{"name":"name3","group":"group1","id":"789", ...}];
After I get another array:
var array1 = [{"name":"name1","group":"group1","id":"123", ...},
{"name":"name4","group":"group1","id":"987", ...}]
I need to push items from second array into first, but how can I check if first array contains objects from second array?
Each object in array contain more property and some of them are created dynamically so I can't check for example by indexOf(). All solutions that I found works only with simple objects like Int. It will be great if I could check by property "id" for example.
Use find first
var newObj = {"name":"name2","group":"group2","id":"456"};
var value = array.find( s => s.id == newObj.id );
Now push if the value is not found
if ( !value )
{
array.push( newObj )
}
(More generic)you can do this one line using following (which will add all object which is not in array).
array.concat(array1.filter(x=>!array.find(s=>s.id==x.id)));
var array = [{"name":"name1","group":"group1","id":"123"},
{"name":"name2","group":"group2","id":"456" },
{"name":"name3","group":"group1","id":"789"}];
var array1 = [{"name":"name1","group":"group1","id":"123"},
{"name":"name4","group":"group1","id":"987"}];
array=array.concat(array1.filter(x=>!array.find(s=>s.id==x.id)));
console.log(array);
I'm getting output: [{"ref":"contact.html","score":0.7071067811865475}]
$.getJSON( "index.json", function(content) {
idx = lunr.Index.load(content);
var results = idx.search(variabletosearch);
var final = JSON.stringify(results);
console.log(final);
});
How can I print value of ref? When I console.log(final[0].ref); I get undefined.
EDIT:
JSON.stringify returns a string, not an object. So in this case 'final' is a string that contains the same data that was in the object 'results'
To access the data from an object, you can use result[0].ref, or if you want to use 'final' (although you don't need to), you can do this:
final = JSON.parse(final)
console.log(final[0].ref)
If it's only one object within the array, then the other answers are enough, but since arrays are used to store multiple objects, you can do this as follows:
var arr = [
{"ref": "object1", "score": "1"},
{"ref": "object2", "score": "2"}
]
arr.map(function(object) {
console.log(object.ref)
})
JSFiddle using an alert instead of console.log()
You can also use a loop, but this cleaner.
var a = [{"ref":"contact.html","score":0.7071067811865475}];
a[0].ref;
a[0] is the '0'th (or first) element in the array which is the object literal {"ref":"contact.html","score":0.7071067811865475} from here you can access the object normally using dot notation.
Expanded out a bit:
var a = [{"ref":"contact.html","score":0.7071067811865475}];
var myObject = a[0];
console.log(myObject.ref);
//or with null checking
if (myObject) {
console.log(myObject.ref ? myObject.ref : 'no value');
}
Well, assuming
var myvar = [{"ref":"contact.html","score":0.7071067811865475}];
then:
var myref = myvar[0].ref;
I have an array:
var arr = Array()
I wish to make this a multidimensional array, but I wish to pass in the keys dynamically.
Is there a way to do this?
p.addArrayKey = function(key){
arr.key.push('something');
}
You have not really explained what you mean by "multidimensional array". Multidimensional means that your elements would need to be accessed via more than one index. Example:
arr[ 3, 4 ] = ...; // tells us that arr is a 2-dimensional array
arr[ 4, 5, 1 ] = ..; //.....3-dimensional array
arr[ key ] = 'something'; // is a one-dimensional array!!
But yes, you can use a key as an index as follows. You cannot use the dot notation because key is a variable. And since you have the index, key, you don't use push but you can assign the value directly:
arr[ key ] = 'something';
So that your method is:
p.addArrayKey = function(key, something){
arr[ key ] = something;
};
And you can call it like so:
p.addArrayKey ( 'mykey', 'something' );
And the output would be:
[mykey: "something"]
WORKING JSFIDDLE DEMO
However if something is the key you want to create in the array:
arr.something = 'initial value'; // or
arr[ 'something' ] = 'initial value'; //
Should work just fine.
I currently have a problem in deleting entries from an associative array in JS.
I tried this:
myArray['key'] = value;
myArray['key1'] = value1;
...
delete myArray['key'];
But I get following results in my application:
[ undefined, { key1: 'value1', key2: 'value2' }, undefined,
{ key1: 'value1', key2: 'value2' }, undefined, undefined ]
How can I delete the whole entry, key and value? I found the method splice() but I think it uses a different index. I wasn't able to delete the entries I want by passing the key to splice().
It seems you are mixing arrays and objects. Associative arrays should be realized with objects:
myArray = {};
myArray['key'] = value;
myArray['key1'] = value1;
It is a bit confusing though because in your output, the objects don't have key anymore (so it worked), but the array containing those objects as undefined values. I cannot see how
delete myArray['key']; is related to your output and which variable now contains which value (please clarify).
But it looks like you did something like:
var container = new Array(6);
container[1] = myArray;
container[3] = myArray;
This will initialize the array with 6 undefined values (sort of) and then set the second and forth value to something else.
If you want to use that "array" as associative array, you should declare it as object too:
var container = {};
Please post more code if you need a better answer.
Update: Yes, you should declare displayedWidgets as object:
var widgets = {
displayedWidgets: {},
clear: function() {
this.displayedWidgets = {};
},
add: function(widget) {
this.displayedWidgets[widget.id] = widget;
},
addArray: function(newWidgets) {
// note that `each` is only available in newer browsers,
// just loop over the array
for(var i = newWidgets.length; i--; ) {
this.add(newWidgets[i]);
}
},
remove: function(widgetId) {
if (widgetId in this.displayedWidgets) {
delete this.displayedWidgets[widgetId];
}
}
};
Is there an elegant way to access the first property of an object...
where you don't know the name of your properties
without using a loop like for .. in or jQuery's $.each
For example, I need to access foo1 object without knowing the name of foo1:
var example = {
foo1: { /* stuff1 */},
foo2: { /* stuff2 */},
foo3: { /* stuff3 */}
};
var obj = { first: 'someVal' };
obj[Object.keys(obj)[0]]; //returns 'someVal'
Object.values(obj)[0]; // returns 'someVal'
Using this you can access also other properties by indexes. Be aware tho! Object.keys or Object.values return order is not guaranteed as per ECMAScript however unofficially it is by all major browsers implementations, please read https://stackoverflow.com/a/23202095 for details on this.
Try the for … in loop and break after the first iteration:
for (var prop in object) {
// object[prop]
break;
}
You can also do Object.values(example)[0].
You can use Object.values() to access values of an object:
var obj = { first: 'someVal' };
Object.values(obj)[0]; // someVal
Use Object.keys to get an array of the properties on an object. Example:
var example = {
foo1: { /* stuff1 */},
foo2: { /* stuff2 */},
foo3: { /* stuff3 */}
};
var keys = Object.keys(example); // => ["foo1", "foo2", "foo3"] (Note: the order here is not reliable)
Documentation and cross-browser shim provided here. An example of its use can be found in another one of my answers here.
Edit: for clarity, I just want to echo what was correctly stated in other answers: the key order in JavaScript objects is undefined.
A one-liner version:
var val = example[function() { for (var k in example) return k }()];
There isn't a "first" property. Object keys are unordered.
If you loop over them with for (var foo in bar) you will get them in some order, but it may change in future (especially if you add or remove other keys).
The top answer could generate the whole array and then capture from the list. Here is an another effective shortcut
var obj = { first: 'someVal' };
Object.entries(obj)[0][1] // someVal
Solution with lodash library:
_.find(example) // => {name: "foo1"}
but there is no guarantee of the object properties internal storage order because it depends on javascript VM implementation.
Here is a cleaner way of getting the first key:
var object = {
foo1: 'value of the first property "foo1"',
foo2: { /* stuff2 */},
foo3: { /* stuff3 */}
};
let [firstKey] = Object.keys(object)
console.log(firstKey)
console.log(object[firstKey])
if someone prefers array destructuring
const [firstKey] = Object.keys(object);
No. An object literal, as defined by MDN is:
a list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}).
Therefore an object literal is not an array, and you can only access the properties using their explicit name or a for loop using the in keyword.
To get the first key name in the object you can use:
var obj = { first: 'someVal' };
Object.keys(obj)[0]; //returns 'first'
Returns a string, so you cant access nested objects if there were, like:
var obj = { first: { someVal : { id : 1} }; Here with that solution you can't access id.
The best solution if you want to get the actual object is using lodash like:
obj[_.first(_.keys(obj))].id
To return the value of the first key, (if you don't know exactly the first key name):
var obj = { first: 'someVal' };
obj[Object.keys(obj)[0]]; //returns 'someVal'
if you know the key name just use:
obj.first
or
obj['first']
This has been covered here before.
The concept of first does not apply to object properties, and the order of a for...in loop is not guaranteed by the specs, however in practice it is reliably FIFO except critically for chrome (bug report). Make your decisions accordingly.
I don't recommend you to use Object.keys since its not supported in old IE versions. But if you really need that, you could use the code above to guarantee the back compatibility:
if (!Object.keys) {
Object.keys = (function () {
var hasOwnProperty = Object.prototype.hasOwnProperty,
hasDontEnumBug = !({toString: null}).propertyIsEnumerable('toString'),
dontEnums = [
'toString',
'toLocaleString',
'valueOf',
'hasOwnProperty',
'isPrototypeOf',
'propertyIsEnumerable',
'constructor'
],
dontEnumsLength = dontEnums.length;
return function (obj) {
if (typeof obj !== 'object' && typeof obj !== 'function' || obj === null) throw new TypeError('Object.keys called on non-object');
var result = [];
for (var prop in obj) {
if (hasOwnProperty.call(obj, prop)) result.push(prop);
}
if (hasDontEnumBug) {
for (var i=0; i < dontEnumsLength; i++) {
if (hasOwnProperty.call(obj, dontEnums[i])) result.push(dontEnums[i]);
}
}
return result;
}})()};
Feature Firefox (Gecko)4 (2.0) Chrome 5 Internet Explorer 9 Opera 12 Safari 5
More info: https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Object/keys
But if you only need the first one, we could arrange a shorter solution like:
var data = {"key1":"123","key2":"456"};
var first = {};
for(key in data){
if(data.hasOwnProperty(key)){
first.key = key;
first.content = data[key];
break;
}
}
console.log(first); // {key:"key",content:"123"}
If you need to access "the first property of an object", it might mean that there is something wrong with your logic. The order of an object's properties should not matter.
A more efficient way to do this, without calling Object.keys() or Object.values() which returns an array:
Object.prototype.firstKey = function () {
for (const k in this) {
if (Object.prototype.hasOwnProperty.call(this, k)) return k;
}
return null;
};
Then you can use it like:
const obj = {a: 1, b: 2, c: 3}
console.log(obj.firstKey()) //=> 'a'
This doesn't necessarily return the first key, see Elements order in a "for (… in …)" loop
we can also do with this approch.
var example = {
foo1: { /* stuff1 */},
foo2: { /* stuff2 */},
foo3: { /* stuff3 */}
};
Object.entries(example)[0][1];
This is an old question but most of the solutions assume that we know the attribute's name which it is not the case for example if you are trying to visualize data from files that the user can upload or similar cases.
This is a simple function that I use and works in both cases that you know the variable and if not it will return the first attribute of the object (sorted alphabetically)
The label function receives an object d and extract the key if exits, otherwise returns the first attribute of the object.
const data = [
{ label: "A", value: 10 },
{ label: "B", value: 15 },
{ label: "C", value: 20 },
{ label: "D", value: 25 },
{ label: "E", value: 30 }
]
const keys = ['label', 0, '', null, undefined]
const label = (d, k) => k ? d[k] : Object.values(d)[0]
data.forEach(d => {
console.log(`first: ${label(d)}, label: ${label(d, keys[0])}`)
})
keys.forEach(k => {
console.log(`label of ${k}: ${label(data[0], k)}`)
})
For values like 0, '', null, and undefined will return the first element of the array.
this is my solution
const dataToSend = {email:'king#gmail.com',password:'12345'};
const formData = new FormData();
for (let i = 0; i < Object.keys(dataToSend).length; i++) {
formData.append(Object.keys(dataToSend)[i],
Object.values(dataToSend)[i]);
}
console.log(formData);
Any reason not to do this?
> example.map(x => x.name);
(3) ["foo1", "foo2", "foo3"]
Basic syntax to iterate through key-value gracefully
const object1 = {
a: 'somestring',
b: 42
};
for (const [key, value] of Object.entries(object1)) {
console.log(`${key}: ${value}`);
}
// expected output:
// "a: somestring"
// "b: 42"
As others have pointed out, if the order of properties is important, storing them in an object is not a good idea. Instead, you should use an array via square brackets. E.g.,
var example = [ {/* stuff1 */}, { /* stuff2 */}, { /* stuff3 */}];
var first = example[0];
Note that you lose the 'foo' identifiers. But you could add a name property to the contained objects:
var example = [
{name: 'foo1', /* stuff1 */},
{name: 'foo2', /* stuff2 */},
{name: 'foo3', /* stuff3 */}
];
var whatWasFirst = example[0].name;
For those seeking an answer to a similar question, namely: "How do I find one or more properties that match a certain pattern?", I'd recommend using Object.keys(). To extend benekastah's answer:
for (const propName of Object.keys(example)) {
if (propName.startsWith('foo')) {
console.log(`Found propName ${propName} with value ${example[propName]}`);
break;
}
}