Dictionary get value javascript

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Get value from dictionary in JavaScript by key
Get value from dictionary in JavaScript by key
Get key value of dictionary
How to find value using key in javascript dictionary
How can I get a collection of keys in a JavaScript dictionary? [duplicate]
Everything You Should Know about Javascript Dictionaries

Get value from dictionary in JavaScript by key

Solution 1: In JavaScript dictionaries are objects. You will probably find that the value is there, but the key is an integer.

Get value from dictionary in JavaScript by key

In JavaScript script I have created following dictionary.

var dictionary =[]; $(function () < dictionary.push(< key: @item.Key.ToShortDateString().ToString(), value: @Html.Raw(JsonConvert.SerializeObject(item.Value)), >); alert(dictionary['2017-09-19']); >);

In alert it shows me undefined . How can I read value from this dictionary?

Rather than using an array use an object

$(function () < var dictionary = <>; dictionary[@item.Key.ToShortDateString().ToString()] = @Html.Raw(JsonConvert.SerializeObject(item.Value)); alert(dictionary['2017-09-19']); >);

The variable dictionary is an array which consists of objects. If you want to access you need to access by index.

 var dictionary = []; dictionary.push(< key: '2017-09-19', value: 'test', >); var result = dictionary.filter(function(element) < return element.key == '2017-09-19'; >);if (result.length > 0) < // we have found a corresponding element console.log(result[0].value); >

Get value from dictionary in JavaScript by key, Get value from dictionary in JavaScript by key. Ask Question Asked 4 years, 11 months ago. Modified 4 years, 11 months ago. Viewed 18k times 3 In JavaScript (JsonConvert.SerializeObject to read value by key as a date saved in string. – maciejka. Sep 10, 2017 at 18:23. Code sample$(function () ;dictionary[@item.Key.ToShortDateString().ToString()] = @Html.Raw(JsonConvert.SerializeObject(item.Value));alert(dictionary[‘2017-09-19’]);>);Feedback

Get key value of dictionary

How do I get the value from a javascript dictionary? (I don’t even know if it’s called a dictionary in javascript)

I get the following object (friends) from the facebook sdk. How do I, for example, loop through the names?

In JavaScript dictionaries are objects. To access object properties you may use either dot notation or square brackets notation. To iterate an array you may use simple for loop.

var obj = < data: [< id: "xxxxx", name: "Friend name" >, < id: "xxxxx", name: "Friend name" >] >; for (var i = 0, len = obj.data.length; i

Loop through the data array within the object that wraps the whole thing. Then target the name with object dot notation:

for (var i = 0, l = obj.data.length; i

You can loop through the data array like this:

var obj = , ]>; //loop thru objects in data obj.data.forEach(function(itm) < console.log(itm.name); >);

const obj = < data: [< id: "xxxxx", name: "Friend name" >, < id: "xxxxx", name: "Friend name" >] >obj.data.map(x => console.log(x.name))

Javascript — Get key value of dictionary, How do I get the value from a javascript dictionary? (I don’t even know if it’s called a dictionary in javascript) I get the following object (friends) from the facebook sdk. How do I, for example, Get key value of dictionary. Ask Question Asked 8 years, 10 months ago. Modified 5 years, 10 months ago. …

How to find value using key in javascript dictionary

I have a question about Javascript’s dictionary. I have a dictionary in which key-value pairs are added dynamically like this:

var Dict = [] var addpair = function (mykey , myvalue) [ Dict.push(< key: mykey, value: myvalue >); >

I will call this function and pass it different keys and values. But now I want to retrieve my value based on the key but I am unable to do so. Can anyone tell me the correct way?

var givevalue = function (my_key) < return Dict["'" +my_key +"'"] // not working return Dict["'" +my_key +"'"].value // not working >

As my key is a variable, I can’t use Dict.my_key

Arrays in JavaScript don’t use strings as keys. You will probably find that the value is there, but the key is an integer.

If you make Dict into an object, this will work:

var dict = <>; var addPair = function (myKey, myValue) < dict[myKey] = myValue; >; var giveValue = function (myKey) < return dict[myKey]; >;

The myKey variable is already a string, so you don’t need more quotes.

How to find value using key in javascript dictionary, 1 Answer. Arrays in JavaScript don’t use strings as keys. You will probably find that the value is there, but the key is an integer. var dict = <>; var addPair = function (myKey, myValue) < dict [myKey] = myValue; >; var giveValue = function (myKey) < return dict [myKey]; >; The myKey variable is already a string, so you don’t need …

How can I get a collection of keys in a JavaScript dictionary? [duplicate]

Now, I need to show it in a dropdownlist. How can I get the collection of keys in my dictionary?

Use Object.keys() or shim it in older browsers.

const keys = Object.keys(driversCounter);

If you wanted values , there is Object.values() and if you want key and value, you can use Object.entries() , often paired with Array.prototype.forEach() like this.

Object.entries(driversCounter).forEach((Dictionary get value javascript) => < console.log(key, value); >);

Alternatively, considering your use case, maybe this will do it.

var selectBox, option, prop; selectBox = document.getElementById("drivers"); for (prop in driversCounter)

One option is using Object.keys() :

It works fine for modern browsers (however, Internet Explorer supports it starting from version 9 only).

To add compatible support you can copy the code snippet provided in MDN .

To loop through the «dictionary» (we call it object in JavaScript), use a for in loop:

for(var key in driversCounter) < if(driversCounter.hasOwnProperty(key)) < // key = keys, left of the ":" // driversCounterDictionary get value javascript = value, right of the ":" >>

This will work in all JavaScript implementations:

var keys = []; for (var key in driversCounter) < if (driversCounter.hasOwnProperty(key)) < keys.push(key); >>

Like others mentioned before you may use Object.keys , but it may not work in older engines. So you can use the following monkey patch:

How can I get a collection of keys in a JavaScript, How can I get a collection of keys in a JavaScript dictionary? [duplicate] Ask Question I need to show it in a dropdownlist. How can I get the collection of keys in my dictionary? javascript dictionary. Share. Follow $.each(driversCounter, function(key, value) < keys.push(key); >); …

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Everything You Should Know about Javascript Dictionaries

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Create Dictionaries with Javascript Objects

Javascript Object type offers us enough flexibility to store data as key-value pairs as a standard dictionary does. But its versatility doesn’t end there. Object type also supports accessing stored data using keys, iterating through keys and values, and even using different data types as keys.

And it all starts with creating a new dictionary using Object. Here’s how we can do that.

As an alternative way to create a dictionary, you can first initialize an Object instance and populate it with key-value pairs in the following manner.

  We can take another step ahead and create an object with a null prototype. It removes all the methods inherited from Object.prototype. It suits us the best because these object methods are unnecessary for a dictionary. This includes methods such as hasProperty() , hasOwnProperty() , toString() , valueOf() etc.

Here is how you can modify the Object creation step to get an object with a null prototype.

Javascript allows us to assign different data types—including string, integer, and float—for keys and values, even in the same dictionary.

You can even store a Javascript method as a value in an Object-based dictionary.

However, when storing keys of types other than string, Object implicitly converts them to string type before storing. For example, this is how Javascript has converted the keys of the above dictionary during its creation:

Being able to retrieve a particular key-value pair using the key is one of the most valuable features of the dictionary data structure. With the Javascript Object type, doing this is as easy as the following example shows.

   As this example shows, you can use any key as an index to retrieve the value associated with it. For keys of type string, you can access the value by considering the key as a property of the object.

Iterate Through Key-Value Pairs

Javascript Object type provides several methods to iterate through keys, values, or key-value pairs depending on the use case.

First, let’s see how to iterate through the keys in the dictionary using the Object.keys method.

Iterating through values of the dictionary follows the same pattern with the help of Object.values method.

We can also iterate over pairs of keys and values in the same loop using the Object.entries method.

We can use Javascript’s delete operator to remove a key-value pair from an Object-based dictionary. For example:

One downside to using the delete operator to remove a key-value pair is that it reduces the performance of your code. If you’re more concerned about the performance than completely removing the property from the dictionary, you can set its value to null or undefined to flag a “removed” property.

Even though this method doesn’t entirely remove the property, it completes execution much faster than the delete operator.

With that, we have discussed the basics of creating dictionaries in Javascript with the help of its Object type. In the next section, let’s see how we can get a similar result using ES6 Maps.

Create Dictionaries with Javascript Maps

Javascript Maps, introduced in ES6, are another excellent alternative to use for creating dictionaries. In fact, Maps have an added advantage over regular Objects when it comes to functioning like dictionaries. We have listed some key benefits of using Maps over Objects for this use case below.

Keys in maps can be of any type. It includes objects in addition to the primitive and string types Objects accept as keys. And Maps preserve the initial type of the key without implicitly converting them to strings as Objects does.
A Map orders its key-value pairs in the order we inserted them. But the ordering in Objects is not as reliable and straightforward as Maps.
Maps have a “size” property that directly retrieves the number of stored key-value pairs. With Objects, we have to manually calculate the size with the help of Object.keys or a similar method.

So, how can we create dictionaries with Maps? Let’s find out.

   This returns us a map with its key types preserved.

ES6 Maps provides a dedicated “get” method to retrieve data based on keys. Here’s how we can use it to access stored key-value pairs.

Maps type in Javascript is directly iterable. So, we don’t have to use an additional method like Object.keys to retrieve the set of key-value pairs stored in a map. Instead, we can use a for…of loop to iterate over data like the following code snippet shows.

 Maps also provide separate entries(), keys(), and values() functions to iterate over keys and values in different ways depending on the use case.

Again, Maps have a dedicated method for deleting a stored key-value pair. It returns true if the delete operation completes and false otherwise.

 123, 'registered' => true, 1 => [ 1, 2, 3, 5 ] >

Additional Dictionary Operations with Maps

In addition to what we discussed so far, Maps supports several more methods that allow us to interact with dictionaries. For example, we can use the following has method to check whether the dictionary contains a specific key.

Get the size of the dictionary using size :

Conclusion

Even though Javascript doesn’t have an in-built Dictionary data type, its Object and Map types can behave similarly to dictionaries in languages like Python. In today’s tutorial, we talked about using these alternative types to store and access key-value pairs in Javascript as a standard dictionary does.

So, next time, when you’re looking for something that works like a dictionary to solve a problem, you can choose one of the two options we provided here depending on your requirements.

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