Using a Javascript Map as data in D3-CodePudding

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. I'm not getting any errors, it's just not creating them.

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())));

EDIT: Not working either. Does not create any rect on svg with id of demo1. I know they would overlap at this point. Also hovering over d in chrome dev tools shows nothing. data is available The code:

 function createNoteRectOnStaff()
{
    let data = new Map(JSON.parse(localStorage.testMusic));
    d3.select("#demo1")
    .selectAll("rect")
    .data(data,d=>d)
    .enter()
    //.join("rect")
    .append("rect")
    //.attr('id',d=> d[0]) 
    .attr('x', 30)
    .attr('y', 60)
    .attr('width', 30)
    .attr('height', 60)
    .attr('stroke', 'green')
    .attr('stroke-linecap', 'butt')
    .attr('stroke-width', '1')
    .attr('fill', 'black')
    

}

...

I tried this also:

.data(d3.keys(data))

but when I step into that d3 function, it doesnt recognized them either.

CodePudding user response：

You can use data(music) or data(music, d => d) and extract data from the Map per the example below.

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"});

d3.select("body")
  .selectAll(".item")
  .data(music, d => d) // or just .data(music)
  .enter()
  .append("p")
  .text(d => {
    const key = d[0];
    const str = d[1].str;
    const fret = d[1].fret;
    return [key, str, fret].join(" : ");
  });

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/7.0.0/d3.min.js"></script>

In the source for data.js there is a function called arraylike that will return an array from a Map with Array.from(Map) which (I assume) is what is at play here. You can see a simple Array.from(music):

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"});

console.log(Array.from(music));

.as-console-wrapper { max-height: 100% !important; top: 0; }