I am trying to read fiexd size array from branches in TTree in jsroot. At first, I built a tree with C++ and coded like
// in cpp
tree.Branch("px", &px, "px[3]/D");
So this branch is a fixed size array branch. And I am familiar to read this branch with C++, but I failed to read it with jsroot. I followed the demo in Reading object from the ROOT file, and coded like
// in main.js script
class MySelector extends TSelector {
constructor() {
super();
this.addBranch('px');
}
...
}
This works well with bracnhes that store single number. But it failed with array. To run the above js code, I build a simple local server on win10 with command python -m http.server, serving a webpage writring with html. In the webpage, I use
# in html
<script type="module" src="main.js"></script>
to run the code I memtioned above. I check the webpage with firefox browser. I tried to get more information about the variable px using codes
console.log(this.tgtobj.px, typeof(this.tgtobj.px));
The log shows that px is of number type, and I can only get px[0]. However, I hope to read it as Array type in js to get the information of px[1] and px[2].
ROOT Version: jsroot 7.5.2
Platform: win10
Compiler: firefox?
------------ update 1 -------------------
I upload the root file (example.root), html (index.cpp) and javascript code (main.cpp). Since the limited of extensions, please change the name of the files by yorurself (index.cpp → index. html, main.cpp → main.js).
example.root (5.6 KB)
index.cpp (248 Bytes)
main.cpp (698 Bytes)
#include <TFile.h>
#include <TTree.h>
int main() {
TFile opf("example.root", "recreate");
TTree opt("tree", "example tree");
// output data
double px[3];
double p;
// setup output branches
opt.Branch("px", px, "px[3]/D");
opt.Branch("p", &p, "p/D");
// fill data
for (int i = 0; i < 10; ++i) {
px[0] = i;
px[1] = i+1;
px[1] = i+2;
p = px[0] + px[1] + px[2];
opt.Fill();
}
// save tree
opt.Write();
// close files
opf.Close();
return 0;
}
To be clear, I paste the C++ code that building this example root file.
