Как можно реализовать методы shift, unshift, reverse, includes, indexOf, lastIndexOf, reverse?

Array.prototype.shift = function () {
  if (this.length === 0) {
    return;
  }
  let result = this[0];
  for (let i = 1; i < this.length; ++i) {
    this[i - 1] = this[i];
  }
  this.length--;
  return result;
}
 
Array.prototype.unshift = function(...args) {
  if (args.length === 0) {
    return this.length;
  }
  for (let i = this.length - 1 + args.length; i >= args.length; --i) {
    this[i] = this[i - args.length];
  }
  for (let i = 0; i < args.length; ++i) {
    this[i] = args[i];
  }
  return this.length;
}
 
Array.prototype.reverse = function() {
  let tmp;
  for (let i = 0; i < this.length / 2; ++i) {
    tmp = this[i];
    this[i] = this[this.length - i - 1];
    this[this.length - i - 1] = tmp;
  }
  return this;
}
 
Array.prototype.includes = function(searchElement) {
  for (let i = 0; i < this.length; ++i) {
    if (this[i] === searchElement) {
      return true;
    }
  }
  return false;
}
 
Array.prototype.indexOf = function(searchElement) {
  for (let i = 0; i < this.length; ++i) {
    if (this[i] === searchElement) {
      return i;
    }
  }
  return -1;
}
 
Array.prototype.lastIndexOf = function(searchElement) {
  for (let i = this.length - 1; i >= 0; --i) {
    if (this[i] === searchElement) {
      return i;
    }
  }
  return -1;
}

Array.prototype.includes = function(searchElement, fromIndex = 0) {
  if (this.length === 0) return false;
  if (fromIndex >= this.length) return false;
  if (fromIndex < 0) fromIndex = this.length + fromIndex > 0 ? this.length + fromIndex : 0;
  for (let i = fromIndex; i < this.length; i++) {
    if (this[i] === searchElement) {
      return true;
    }
  }
  
  return false;
}
 
Array.prototype.indexOf = function(searchElement, fromIndex = 0) {
  if (this.length === 0) return -1;
  if (fromIndex >= this.length) return -1;
  if (fromIndex < 0) fromIndex = this.length + fromIndex > 0 ? this.length + fromIndex : 0;
  for (let i = fromIndex; i < this.length; i++) {
    if (this[i] === searchElement) {
      return i;
    }
  }
  
  return -1;
}
 
Array.prototype.lastIndexOf = function(searchElement, fromIndex = this.length - 1) {
  if (this.length === 0) return -1;
  if (this.length + fromIndex < 0) return -1;
  if (fromIndex >= this.length) fromIndex = this.length - 1;  
  if (fromIndex < 0) fromIndex = this.length + fromIndex;
  for (let i = fromIndex; i >= 0; i--) {
    if (this[i] === searchElement) {
      return i;
    }
  }
  
  return -1;
}