Annotating Types

Annotating declarations and casts

The compiler recognizes @type and function declarations (@param, @return, etc) annotations in two contexts: declarations and casts.

Variable and functions can be declared with either traditional declarations, or inline declarations, which are more concise.

Examples

Function declarations

    /** @type {function(number):string} */
    function f(x) {return x + ' apples'}

or the more concise inline function declaration:

    function /** string */ f(/** number */ x) {return x + ' apples'}

Variable declarations

    /** @type {string} */
    var x = 'fruit';

or the more concise inline var declaration:

    var /** string */ x = 'fruit';

Property declarations

    /** @type {string} */
    x.prop = 'fruit';

or

    var x = {
      /** @type {string} */
      prop : 'fruit'
    };

Catch declarations

    try { 
      ... 
    } catch (/** @type {string} */ e) {
      ...
    }

Type Casts

Type cast precede a parenthesized expression.

    var x = /** @type {string} */ (fruit);