JSFiddle - React, Tailwind, and code Playground

JavaScript

var x = [{
    "id": "id2",
    "index": "2",
    "str": "str2",
    "cent": "200",
    "triplet": "222"
},
{
    "id": "id3",
    "index": "3",
    "str": "str3",
    "cent": "300",
    "triplet": "333"
},
{
    "id": "id4",
    "index": "4",
    "str": "str4",
    "cent": "400",
    "triplet": "444"
},
{
    "id": "id5",
    "index": "5",
    "str": "str5",
    "cent": "500",
    "triplet": "555"
}];

// Iterate thorugh the array
[].forEach.call(x, function(inst, i){
	// Iterate through all the keys
    [].forEach.call(Object.keys(inst), function(y){
        // Check if string is Numerical string
       	if(!isNaN(x[i][y]))
            //Convert to numerical value
        	x[i][y] = +x[i][y];
    });
    
});

console.log(x);