Using a Javascript Map as data in D3

I’m trying to set the datum of svg rectangles using a js Map, but it isnt working. I think the “d.key” is wrong but not sure. I want the map key to be the data at this point.

The data:

    const music = new Map();
    music.set("2345",{str:"4",fret:"6"});
    music.set("5478",{str:"5",fret:"2"});
    music.set("4317",{str:"4",fret:"3"});
    music.set("3455",{str:"5",fret:"12"});
    localStorage.setItem("testMusic",JSON.stringify(Array.from(music.entries())));

The code (partial):

let data = new Map(JSON.parse(localStorage.testMusic));
//let data = localStorage.getItem("testMusic");
d3.select("#demo1")
.selectAll("rect")
.data(data,function(d) { return d.key})
.enter()
.append('rect')

…