Let's implement TradingView's Advanced Real-Time Chart Widget in NextJS.
components for reusable components
pages NextJS pages
public public assets. We put the Charting Library files in /public/lib/trading_view in this folder. The lib folder may be gitignored. Please check and and ask for the access.
src for helper functions, core constants, global custom hooks, redux-toolkit folder and a file for global types.
styles for .sass files.
We start our charting functions from /src/hooks/useTradingView.ts file. Let's open the file and read through.
The Arguments:
widgetOptions is the setup object. Required.
depsArr is the dependency array for the useEffect. It'll be an empty array if you don't want to re-initiate the chart on anything. Required.
applyOverrides an optional object used for the styling of the main chart background and bars.
First we create a function named chartinit, which gets an argument which will be the widgetOptions we took as an argument for this custom hook. In the function we store the widget constructor in a variable and later we add the variable in the global window object as tvWidget. This new object has many methods attached to it. Here's the list of the methods in the interface ChartingLibraryWidgetOptions. We worked on the onChartReady and applyOverrides inside this.
Inside the useEffect we first made the tvWidget null so it doesn't keep anything from the past. Then we call out chartInit function. At last we write our cleaner function.
Finally we return the depsArr which we got from the argument. It's optional.
Notes 📝
The arguments of the custom hooks are in an object.
window.tvWidget is not giving ts error because in the /src/globalTypes.ts file we added tvWidget in the global namespace in window object.
In the Chart Component file, we only have a div that has a ref, id and some styling. We get the id and ref from the useChart hook file. The useChart hook is the place where we customize the chart.
👉 Make sure the file is default exported. Named export will give build error.
useChartFrom the line 25-40, we mainly have some variables and helper functions. Then we see some objects.
applyOverrides see applyOverrides
studyOverrides see studyOverrides
timeFrames see timeFrames
widgetOptions see widgetOptions
depsArr the dependency array on which the the char re-initiates.
Apply overrides to the colors of the main chart background and bars. This doesn't override the colors of the top, bottom or side toolbars. See the applyOverrides object in useChart hook which is commented there.
This override object is to set in widgetOptions object for the key studies_overrides. It overrides the colors of the newly created indicators. Example can be found in the studyOverrides object in useChart hook which is commented there for the volume indicator. Others indicators are not properly tested yet.
It's the constructor of the tvWidget that is needed to inititate the chart. Let's talk about the required parameters.
Symbol, interval
Symbol is the symbol for the data fetching. Resolution or interval is a time period of one bar.
Container
The container can either be a reference to an attribute of a DOM element inside which the iframe with the chart will be placed or the HTMLElement itself. It can be useRef or document.getElementById('id') or just the id of the element as an reference.
library_path
The static path of the charting library. Provide the path to the folder, not any file.
datafeed
JS object that implements the JS API. The required methods are:
onReady This call is intended to provide the object filled with the configuration data. Charting Library assumes that you will call the callback function and pass your datafeed configurationData as an argument. Configuration data is an object.
searchSymbols This call is intended to provide the list of symbols that match the user's search query.
resolveSymbol Charting Library will call this function when it needs to get SymbolInfo by symbol name.
getBars This function is called when the chart needs a history fragment defined by dates range.
subscribeBars Charting Library calls this function when it wants to receive real-time updates for a symbol. The Library assumes that you will call onRealtimeCallback every time you want to update the most recent bar or to add a new one.
unsubscribeBars Charting Library calls this function when it doesn't want to receive updates for this subscriber any more. subscriberUID will be the same object that Library passed to subscribeBars before.
To read more about datafeed, go to the datafeed wiki or the datafeed file.
You can see the toolbar at the bottom of the chart. Each of those buttons on the left side switches the chart time frame. Switching time frame means:
You can customize default time frames using the time_frames argument of the widget constructor.