Array.length

Summary

An unsigned, 32-bit integer that specifies the number of elements in an array.

Syntax

array.length

Description

The value of the length property is an integer with a positive sign and a value less than 2 to the 32 power (2³²).

You can set the length property to truncate an array at any time. When you extend an array by changing its length property, the number of actual elements does not increase; for example, if you set length to 3 when it is currently 2, the array still contains only 2 elements.  Also see Relationship between length and numerical properties. The length property says nothing about the number of values in the array.

Examples

Example: Iterating over an array

In the following example the array numbers is iterated through by looking at the length property to see how many elements it has. The value in each element is then doubled.

var numbers = [1,2,3,4,5];

for (var i = 0; i < numbers.length; i++) {
  numbers[i] *= 2;
}
// numbers is now [2,4,6,8,10];

Example: Shortening an array

The following example shortens the array statesUS to a length of 50 if the current length is greater than 50.

if (statesUS.length > 50) {
   statesUS.length=50
}