JSFiddle - React, Tailwind, and code Playground

JavaScript

var grid = {
    "name": "desktop",
    "columns": [
        {
        "id": "icons",
        "width": 50},
    {
        "id": "title",
        "width": 200},
    {
        "id": "name",
        "width": 300},
    {
        "id": "revision",
        "width": 400}
    ]
};

var columns = grid.columns;
var gridName = grid.name;

var colWidths = {};
colWidths[gridName] = {}; 

$.each(columns, function(c) {
    
    var col = columns[c];
    var colname = col.id;
    var colwidth = col.width;
    
    var thisGrid = colWidths[gridName];
    if(!thisGrid[colname]) thisGrid[colname] = 0;
        
    thisGrid[colname] += colwidth;

});

document.write(JSON.stringify(colWidths));
//alert(colWidths.desktop.title);