Tuesday, September 06, 2005

JavaScript: JavaScript has Closures

Python has closures:
def outer():
print "Enter number:",
num = raw_input()
def inner():
print num
return inner

f = outer()
f()
Note that the variable num is available from within inner when outer has already completed.

Did you know that JavaScript has them too?
function testSetTimeout() {
var privateVar = 'A string';
function bar() { alert(privateVar); }
window.setTimeout(bar, 1000);
}

testSetTimeout();
The function bar makes use of privateVar which a variable in testSetTimeout's local scope even though bar is invoked later by setTimeout, i.e. after testSetTimeout has completed.