JSFiddle - React, Tailwind, and code Playground

HTML

<div id="stuff"></div>

JavaScript

var arr=new Array();

var rows=4;
var cols=10;

for(var i = 0; i < rows + cols - 1; i++){
    
    for(var j = Math.min(rows,i+1)-1; j >= Math.max(0,i-cols+1); j--){
        arr.push((j*cols)+i-j);
    }  

}
            
$("#stuff").append(arr+"");