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| -rw-r--r-- | javascript.html.markdown | 17 |
1 files changed, 6 insertions, 11 deletions
diff --git a/javascript.html.markdown b/javascript.html.markdown index bcaf9a29..9b87b022 100644 --- a/javascript.html.markdown +++ b/javascript.html.markdown @@ -185,7 +185,7 @@ do { input = getInput() } while (!isValid(input)) -// the for loop is the same as C and Java: +// the for loop is the same as C and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times @@ -255,24 +255,19 @@ permanent // = 10 // One of JavaScript's most powerful features is closures. If a function is // defined inside another function, the inner function has access to all the -// outer function's variables. +// outer function's variables, even after the outer function exits. function sayHelloInFiveSeconds(name){ var prompt = "Hello, " + name + "!" function inner(){ alert(prompt) } setTimeout(inner, 5000) - // setTimeout is asynchronous, so this function will finish without waiting - // 5 seconds. However, once the 5 seconds is up, inner will still have - // access to the value of prompt. + // setTimeout is asynchronous, so the sayHelloInFiveSeconds function will + // exit immediately, and setTimeout will call inner afterwards. However, + // because inner is "closed over" sayHelloInFiveSeconds, inner still has + // access to the 'prompt' variable when it is finally called. } sayHelloInFiveSeconds("Adam") // will open a popup with "Hello, Adam!" in 5s -// inner() has access to the variable "prompt" strictly because of lexical scope. -// A closure is being demonstrated because the inner() function is being executed -// at a later time, and in fact being executed "outside" the scope where it was -// declared (inside of the implementation of setTimeout()), but yet inner() STILL -// has access to the variable "prompt". It is said that inner() has a "closure" -// over the variables of sayHelloInFiveSeconds(). /////////////////////////////////// // 5. More about Objects; Constructors and Prototypes |