BirthME, Doulas

I’m not exactly sure what you mean by “you can’t pass Maps around as you could with objects”.
If you'd like to contribute to the interactive examples project, please clone The compatibility table in this page is generated from structured data.

Key equality is based on the sameValueZero algorithm. The Map object holds key-value pairs and remembers the original insertion order of the keys. For instance, lets use a phone number for example.

currentValue The current element being processed in the array.

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Where developers & technologists share private knowledge with coworkersProgramming & related technical career opportunitiesyou said that you can turn Map into JSON, why not Map -> JSON -> String?because turning it into JSON in the first place is a slow process and it makes it more costly over all to use Map than an Object even though a Map is faster to iterate over and do calculations. I have a constructor: Also turning it into JSON means to turn it into a string.Native javascript doesn't have any inbuilt serializer.

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Function that is called for every element of arr.Each time callback executes, the returned value is added to new_array.. – user4642212 May 3 '18 at 10:59 But before getting there, let me show you one possible way of using the The array of array that you can see being passed to the So you can rebuild you map in a single line using the following sample code:Thanks for contributing an answer to Stack Overflow! If you’re starting in JavaScript, maybe you haven’t heard of .map(), .reduce(), and .filter().For me, it took a while as I had to support Internet Explorer 8 until a couple years ago. Utility to map one JavaScript object to another. There are two main functions: map and transform.They take a map from one reference list into an object to another reference list, and optionally one or more maps from the value at that location to a new value, and return a function that performs those maps when called on an object. Featured on Meta Sign in to enjoy the benefits of an MDN account. Stack Overflow works best with JavaScript enabled

Working with a single element - Working with a known value in an Object, you can access it directly with the key without the need to use a method, such as Map’s get() .
Syntax let new_array = arr.map(function callback( currentValue[, index[, array]]) { // return element for new_array }[, thisArg]) Parameters callback.

You need use some good library for javascript.Well....the thing with this approach is that it relies on JSON standard...and it is slow. This is an example of a Google Maps JSON file which you might see used to store configuration settings to setup your system and google maps marker info. Stack Overflow for Teams is a private, secure spot for you and I'm using observables and mapping it into json : can striguify it but cannot parse it beacuse it's a json already : this.service.getscore() .map(res => res.json()) .map(v => v._items[0].score) .subscribe(data => { this.sc = data }); – user2243952 May 20 '17 at 3:30 Any value (both objects and primitive values) may be used as either a key or a value.. JSON - Objects work flawlessly with JSON.parse() and JSON.stringify(), two essential functions for working with JSON, a common data format that many REST APIs deal with. Certain functions within my Javascript rely on the specific type of object I am using. These habits may lead to confusing behaviors.One alternative output of the map method being called with Get the latest and greatest from MDN delivered straight to your inbox.The newsletter is offered in English only at the moment. The Overflow Blog

It will look like [key, value].To avoid writing any looping code yourself, you can use Now, that's not even the coolest part.

When using AJAX, I tend to pass objects from my server to Javascript in the form of JSON objects (aka Javascript). no it's not a string.

I am asking for a way to turn it into a string without using the JSON format..any other format will suffice as long as it doesnt create N new arrays and stringify every single one of them.

Map.entries returns a new array for each value...so if you have 1000 values....you end up with 1000 arrays..and then you JSON every single one of them...this way is soo slow it makes it useless to use Maps in the first place.

Free 30 Day Trial Certain functions are also commonly used with one argument, even though they take additional optional arguments. You could use JSON.stringify([...map.entries()]) for serializing and new Map(JSON.parse(string)) for parsing. your coworkers to find and share information.

That’s the only way you could serialize maps: turning it into a string.