JavaScript Declarations and Assignments Declaration
Example
There are four principle ways to declare a variable in JavaScript: using the var, let or const keywords, or without a keyword at all ("bare" declaration). The method used determines the resulting scope of the variable, or reassignability in the case of const.
- The
varkeyword creates a function-scope variable. - The
letkeyword creates a block-scope variable. - The
constkeyword creates a block-scope variable that cannot be reassigned. - A bare declaration creates a global variable.
var a = 'foo'; // Function-scope
let b = 'foo'; // Block-scope
const c = 'foo'; // Block-scope & immutable reference
Keep in mind that you can't declare constants without initializing them at the same time.
const foo; // "Uncaught SyntaxError: Missing initializer in const declaration"
(An example of keyword-less variable declaration is not included above for technical reasons. Continue reading to see an example.)
