Working with objects
※ Download: Javascript use variable as object key
This seems an odd request at first but it comes up frequently if you need to query or filter the data in any way using map, find or filter functions for example. The same way, JavaScript objects can have properties, which define their characteristics.
The button's onclick event handler uses this. See for detailed information. But the interface to do this really sucks because a map is not really a good structure to filter or search because of the clunky object parsing interface you have to go through.
Working with objects - Objects are assigned and copied by reference.
I am trying to create a new object with nested value pairs. My initial challenge is that I have a huge object containing lots of junk data, and I'd like to strip away the value pairs that I do not need as well as renaming certain values. Performance is vital as this will iterate over thousands of items. I assume that creating a new object gives better performance than deleting and replacing values within the original object. This might be trivial for smaller objects, but for thousands of records and possibly nested objects, this isn't right. Though you do create lesser code by reconstructing a new object, but not done right, you might end up eating more memory. Been there, not good user experience. Use the almighty server If you are getting this data from the server, it's better that the server handle this operation. Servers are usually faster than the browser, use it to your advantage. That way, you do less on the browser, and prioritize more important tasks, like giving the user a good UI and fast interaction. Doing it all client side Now if you can't do it somewhere else but the server, there are ways to speed it up, or at least not freeze the server. Keep them small Keeping your loops small. I usually notice a significant lag when iterations go more than 500 it's not a magical number, just an observation. Keep your loops small, and avoid that long freeze. Chunk it up In addition to keeping the data small, if you have more data to churn than just the 500, consider using timers. Timers with 1ms intervals don't really execute 1ms later. They execute at least 1ms later, and when JS is not busy. You can use that to your advantage and schedule short tasks at intervals without breaking the UI. Of course, the operation becomes asynchronous, so you might want to build a crude callback system for this. },0 ; Keep the data flat Nesting introduces more complexity to the data. Say you have an array of 10 objects. If you loop through that array, it's just 10 iterations. But what if that 10 items have 5 nested properties that you also want to loop through. So thats 5 nested properties times 10 items, giving you 50. Nesting more will introduce more iterations. Use a library Some of the bright minds in the development world might have already developed functionality similar to what you are Trying to do. Don't reinvent the wheel. In fact, you are doing something similar to Underscore's. That's a very interesting and helpful reply, you made me reconsider the strategy of creating a new object versus modifying the existing object. Server side - I would do the whole process serverside if possible, but there are limitations to the JSON-producing REST API that force me to first get the data as XML, then convert it to an javascript object so I can use it with jQuery DataTables plugin. Web Workers seem interesting, although IE 9 support is vital for this process, so that'll have to wait.
See for more information. And depending on how you want the information to be displayed, certain techniques are more advisable for returning results than others. Object properties can be both primitive values, other objects, and functions. If we imagine an object as a cabinet, then a variable is a key to it. For example, suppose you define an object called person as follows: function Person name, age, sex { this. The following functions facilitate some of these tasks. Also, we could use another variable name here instead of key. The following functions facilitate some of these tasks. If you already go for the object initializer when defining a prototype you will probably most of the time choose the first form. This defines a property that is shared by all objects of the specified type, rather than by just one instance of the object. An object literal is a list of name:value pairs like age:50 inside curly braces . My javascript use variable as object key challenge is that I have a huge object containing lots of junk data, and I'd like to strip away the value pairs that I do not need as well as renaming certain values.
