6.2. Looping Through an Array

Problem

You want to access or process all of the elements of an array in sequential order.

Solution

Use a for loop that increments an index variable from 0 to Array. length - 1. Use the index to access each element in turn.

Discussion

To access the values stored in the elements of an array, loop through the array’s elements using a for loop. Because the first index of an array is 0, the index variable in the for statement should start at 0. The last index of an array is always 1 less than the length property of that array. Within the for statement, you can use the loop index variable within square brackets to access array elements. For example:

myArray = ["a", "b", "c"];
for (var i = 0; i < myArray.length; i++) {
  // Display the elements in the Output window.
  trace("Element " + i + ": " + myArray[i]);
}

The looping index variable (i in the example code) should range from 0 to one less than the value of the length property. Remember that the last index of an array is always one less than its length.

Alternatively, you can also use a for statement that loops backward from Array. length - 1 to 0, decrementing by one each time. Looping backward is useful when you want to find the last matching element rather than the first (see Recipe 6.3). For example:

myArray = ["a", "b", "c"];
for (var i = myArray.length - 1; i >= 0; i--){
  // Display the elements in the Output window in reverse order.
  trace("Element " + i + ": " + myArray[i]);
}

There are many examples in which ...

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