Jump to:

Our volunteers haven't translated this article into ไทย yet. Join us and help get the job done!
You can also read the article in English (US).

The current context of execution. The context in which values and expressions are "visible," or can be referenced. If a variable or other expression is not "in the current scope," then it is unavailable for use. Scopes can also be layered in a hierarchy, so that child scopes have access to parent scopes, but not vice versa.

A function serves as a closure in JavaScript, and thus creates a scope, so that (for example) a variable defined exclusively within the function cannot be accessed from outside the function or within other functions. For instance, the following is invalid:

function exampleFunction() {
    var x = "declared inside function";  // x can only be used in exampleFunction
    console.log("Inside function");
    console.log(x);
}

console.log(x);  // Causes error

However, the following code is valid due to the variable being declared outside the function, making it global:

var x = "declared outside function";

exampleFunction();

function exampleFunction() {
    console.log("Inside function");
    console.log(x);
}

console.log("Outside function");
console.log(x);

Learn more

General knowledge

Document Tags and Contributors

ป้ายกำกับ: 
ผู้มีส่วนร่วมกับหน้านี้: thekosiguy, MohamedAlFahim, irenesmith, sideshowbarker, welm, hbloomer, klez, Andrew_Pfeiffer, kscarfone, panaggio
อัปเดตล่าสุดโดย: thekosiguy,