Can you explain why the alert displays "AAA" instead of "BBB"?
var z = "AAA";
function xx() {
var z = "BBB";
yy();
}
function yy() {
alert(z);
}
xx();
Can you explain why the alert displays "AAA" instead of "BBB"?
var z = "AAA";
function xx() {
var z = "BBB";
yy();
}
function yy() {
alert(z);
}
xx();
Here's a breakdown of how this code functions:
var a = "AAA"; // Set global variable a to "AAA"
function b() {
var a = "BBB"; // Set local variable a to "BBB"
c(); // Call function c
}
function c() {
alert(a); // Alert the global variable a
}
b(); // Call function b
When var z = "BBB" is declared in a function, specifically within the context of xx, it remains local to that function. This is why when yy accesses the variable, it displays "AAA."
The reason for this issue is that by re-declaring the variable z within the function.
function xx() {
var z = "BBB";
yy();
}
Now, the scope of z is limited to the function xx()
If you wish to update the global variable z, you should instead do:
function xx() {
z = "BBB";
yy();
}
Here is a demonstration of how you can achieve the desired functionality, but it is important to note that relying on global variables is not recommended as it goes against best practices in programming.
window.z = "AAA";
function xx() {
window.z = "BBB";
yy();
}
function yy() {
alert(window.z);
}
xx();
A similar approach can be taken in PHP...
<?php
$z = "AAA";
function xx() {
global $z;
$z = "BBB";
yy();
}
function yy() {
global $z;
echo $z;
}
xx();
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