Reverse words in sentence in JavaScript without using JS pre built functions

reverseString.js

let string = "NodeJS is single threaded";
let array = [];
let ress = "";
let reversed = "";
let tempVal = "";
let str = string ;

for (let index = 0; index < str.length; index++) {
  if (str[index] != " " || (index +1) === (str.length)) {
    tempVal += str[index];
    if(index+1===str.length){
      array.push(tempVal);
    let reversed = "";
    for (let value of tempVal) {
      reversed = value + reversed;
    }
    ress += " " + reversed;
    tempVal = "";
    }
  } else {
    array.push(tempVal);
    let reversed = "";
    for (let value of tempVal) {
      reversed = value + reversed;
    }
    ress += " " + reversed;
    tempVal = "";
  }
  reversed = str[index] + reversed;
}
console.log("result: ",ress);