how to split array as per fixed length, and ionic two dates differences in min,seconds,hours

this.forsasi -->array

var perChunk = 5 // items per chunk

var inputArray = this.forsasi;

this.result = inputArray.reduce((resultArray, item, index) => {

const chunkIndex = Math.floor(index/perChunk);

if(!resultArray[chunkIndex]) {

resultArray[chunkIndex] = [] // start a new chunk

}

resultArray[chunkIndex].push(item);

return resultArray

}, [])

console.log(this.result);

this.d1 = JSON.parse(localStorage.getItem("starttime"));

var d2 = new Date(this.d1);

console.log(d2)

var date1 = new Date();

var Str1 =

("00" + (date1.getMonth() + 1)).slice(-2)

+ "/" + ("00" + date1.getDate()).slice(-2)

+ "/" + date1.getFullYear() + " "

+ ("00" + date1.getHours()).slice(-2) + ":"

+ ("00" + date1.getMinutes()).slice(-2)

+ ":" + ("00" + date1.getSeconds()).slice(-2);

console.log(Str1);

var d3 = new Date(Str1);

console.log(d3.getTime(), "d3.getTime()");

var diff1 = (d3.getTime() - d2.getTime()) / 1000; //seconds

console.log(diff1);

// diff1 /= 60; //mintues

//by 1000×60×60 convert to hour