I was wondering about the side effects of calling some of the array methods.
Specifically, consider steps 4, 9, from the 'pop' method:
15.4.4.6 Array.prototype.pop ( )
The last element of the array is removed from the array and returned.
1. Call the [[Get]] method of this object with argument "length".
2. Call ToUint32(Result(1)).
3. If Result(2) is not zero, go to step 6.
4. Call the [[Put]] method of this object with arguments "length" and
Result(2).
5. Return undefined.
6. Call ToString(Result(2)-1).
7. Call the [[Get]] method of this object with argument Result(6).
8. Call the [[Delete]] method of this object with argument Result(6).
9. Call the [[Put]] method of this object with arguments "length" and
(Result(2)-1).
10. Return Result(7).
NOTE
The pop function is intentionally generic; it does not require that its this
value be an Array object. Therefore it can be transferred to other kinds of
objects for use as a method. Whether the pop function can be applied
successfully to a host object is implementation-dependent.
The side effect is as follows: if "this" does not have a "length" property, it
ends up getting one; if "this" does have a length property, but is not an
Array, that "length" property will get updated.
What is the rationale for this?
Example:
<script>
function pizza() {}
var p = new pizza();
document.write("p.length: " + p.length + "<br>");
Array.prototype.pop.call(p);
document.write("p.length: " + p.length + "<br>");
function bridge(len) {
this.length = len;
}
var b = new bridge(2);
document.write("b.length: " + b.length + "<br>");
Array.prototype.pop.call(b);
document.write("b.length: " + b.length + "<br>");
</script>
pratap
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