JSFiddle - React, Tailwind, and code Playground
JavaScript
var arr = ['markdown', ['para', 'This is a ', ['em', 'paragraph']],
['hr'],
['para', 'another paragragh']
];
var len = arr.length;
for(var i = 0; i < len; i++){
if(arr[i].length > 0 && arr[i][0] === 'hr' && i+1 < len){
console.log(arr[i+1]);
//or
for(var j = 0; j < arr[i+1].length; j++){
console.log(arr[i+1][j]);
}
}
}