一個return表達式可以返回也可以不返回一個值表達式： > A return expression can come with or without an value expression: ~~~ return; return expression; ~~~ 它會離開它被聲明所在的控制流最深的函數，當局部函數（第5.11節）被調用時需要被區別： > It leaves the control-?ow of the innermost function it is declared in, which has to be distinguished when local functions (5.11) are involved: ~~~ function f1() { function f2() { return; } f2(); expression; } ~~~ return會離開局部函數 f2，但不會離開 f 1，意味著 expression仍然會被執行。 > The return leaves local function f2, but not f1, meaning expression is still evaluated. 如果 return 不帶值表達式使用，類型工具確保函數返回類型會返回Void 。如果它有一個值表達式，類型工具 統一（第3.5節）它的類型為它所返回的函數的返回類型（顯式指定或者通過前面的return表達式推斷）。 > If return is used without a value expression, the typer ensures that the return type of the function it returns from is of Void. If it has a value expression,the typer uni?es(3.5) its type with the return type (explicitly given or inferred by previous return expressions) of the function it returns from.