读取巨大的csv文件，并使用d3在Javascript中填充地图

Question

I am using d3 to load a huge CSV file which I later use for some processing. I want to load the file and populate a Map based on certain conditions.

The csv file that I have is like this

h1    h2    h3    h4
1     A     3     4
2     A     1     6
1     B     5     7
2     C     8     19

and so on. There may be about 4M+ entries.

I want to populate a Map from this csv data. The map should be like this

1 A : [3, 4]
2 A : [1, 6]
1 B : [5, 7]
2 C : [8, 19]

The key must be the combination of h1 and h2 . Other columns are added as values.

I was able to achieve this using the following codes

function makeKey(a, b) {

    return "" + a + " " + b;
}

function csvToColumnArrays(csv) {

    let csvMap = new Map();

    for (let i = 0; i < csv.length; i++) {


        let data = csv[i];

        let value = [];
        value.push(parseFloat(data["h3"]));
        value.push(parseFloat(data["h4"]));

        let key = makeKey(data["h1"], data["h2"]);

        csvMap.set(key, value);

    }

    return csvMap;

}




d3.csv(file_url, function(csv) {

    let csvMap = csvToMap(csv);

}

This was working perfect files of size 2M entries. But when the size is further increased, the page snaps.

Is there a more efficient way to do this.?

Answer 1

Making a dictionary with 4M entries does not crash my computer.

 var count = 4 * 1000 * 1000; var map = {} for (var i=0; i < count; ++i) { map["" + i + "ABCDEF"[i%6] ] = [ Math.random(), Math.random() ]; } //console.log(map); console.log("done!"); 

With new Map()

 var count = 4 * 1000 * 1000; var map = new Map(); for (var i=0; i < count; ++i) { map.set("" + i + "ABCDEF"[i%6], [ Math.random(), Math.random() ]); } //console.log(map); console.log("done!");