JavaScript - Is there a way to iterate an array from a specific position?

Javascript doesn't have that sugar syntax for the for loop. The method exists .forEach(), but it will always traverse the array in an increasing direction. Similarly you have for(let i of array) {...}to loop through iterables (which would be the closest to what you're looking for, but you can't reverse it)

const array=[0,1,2,3,4,5,6];

for (let i=array.length - 1; i >= 0; i--) {
  console.log(array[i]);
}

If you don't mind destroying the array, you can do the following:

const array=[0,1,2,3,4,5,6];

while (array.length) {
  console.log(array.pop()); //pop saca del array el último elemento
}

A third option would be to add a new method to Array that is the equivalent of .forEach() but in reverse:

const array = ['Hola',1,2,3,4,5,6];

Array.prototype.inverseForEach = function(callback) {
  for (let i=this.length -1 ; i >= -1; i--) {
    callback.call(this,this[i]);
  }
};

array.inverseForEach(console.log);

In general, you have to use a normal for loop to traverse an array or part of it:

for (let index = <valor_inicial>; <condición_a_cumplir>; index = <valor para la siguiente iteración>) {
  ...
}

Although there are many methods to work with them: forEach, reduce, map, some, every, filter ...

In javascript you can use reverse(). It reverses the order of the elements.

arr = [1,2,3,4,5,6,7,8,9,0];
alert(arr.reverse());

I think what you are looking for is the slice (). Returns the selected elements in an array, as a new array object.

The method slice ()selects elements beginning at the given start argument, and ending at, but not including, the given end argument.

Ex:

var frutas = ["Banana", "Naranja", "Limon", "Manzana", "Mango"];
var citricas = frutas.slice(1, 3);
alert (citricas);

If what you want is to print the data in reverse, I leave you the code as an explanation so that the syntax is understood:

To achieve this, you just have to get the length of the array with the length command and just subtract 1 from it (arrays start from position 0, that's why we subtract 1 to get the position of the last element)

 var arr = [1,2,3,4,5,6,7,8,9,0];
    var ultimo=arr.length-1;
    for(var i=ultimo;i>=0;i--){
    	console.log(arr[i])
    }

Explanation: You iterate an array from a position sto a position f(inclusive) and exclude an array of elements, which is , excludeand a function to be executed, which is func.

Array.prototype.iterate = function(s, f, exclude, func) {
 for(; s < f; ++s) {
  var cur = this[s];
  if(check_exclude(exclude, cur)) continue;
  func(cur, s, this);
 }

 function check_exclude(exclude_arr, cur) {
  return exclude_arr.some(exclude_elem => exclude_elem === cur);
 }
};

And you use it like this, I want to print an array ["A", "B", "C", "D", "E"], from index 0to index 3and also skip the B, which is at index 2.

This should show me: A C D, and check that it works:

Array.prototype.iterate = function(s, f, exclude, func) {
     for(; s <= f; ++s) {
      var cur = this[s];
      if(check_exclude(exclude, cur)) continue;
      func(cur, s, this);
     }
     
     function check_exclude(exclude_arr, cur) {
      return exclude_arr.some(exclude_elem => exclude_elem === cur);
     }
    };
    
["A", "B", "C", "D", "E"].iterate(0, 3, ["B"], (cur, i, arr) => {
 console.log(cur);
});

There is no syntax array[::], much less array[:-1]or array[:3].

The only way you could achieve something similar would be through the filter methods and the forEach itself .

Both methods have the same parameters in their callback: currentValue, indexand array(Read the documentation for more information about them).

Both differ in that the filter method will create a new array as long as its true condition is met. While the forEach will do what you ask regardless of whether it is true or false, plus it will overwrite the array.

I leave you some examples of what I tell you. Note that there is a filter that does it for the current element while another one does it for index (specific position of the array).

$(function(){
  arr = [1,2,3,4,5,6,7,8,9,0];
  
  $('#filtere').click(function(){
    $('#resultado').empty();
    let filtrados = arr.filter((element) => element >= 3);
  
    $('#resultado').append(filtrados);
  });
 
  $('#filteri').click(function(){
    $('#resultado').empty();
    let indexFilter = arr.filter((element, index) => index >= 3);
  
    $('#resultado').append(indexFilter);
  });
  
  $('#foreachi').click(function(){
    $('#resultado').empty();
    let texto = '';
    arr.forEach(function (currentValue, index) {
        if (index < arr.length - 3) {
          texto += currentValue;
        }
    });  
  
    $('#resultado').append(texto);
  });
  
});

<button type="button" id="filtere">Clic con filter por elemento</button>
<button type="button" id="filteri">Clic con filter por index</button>
<button type="button" id="foreachi">Clic con forEach por index</button>
<div id="resultado"></div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

You can use the reverse() method in javascript, it will order them backwards

arr = [1,2,3,4,5,6,7,8,9,0];

arr.reverse();

for (var i = arreglo.length - 1; i >= 0; i--) {
    arreglo[i]
}