箭头函数中的花括号 [英] Curly Brackets in Arrow Functions

问题描述

有人可以，请解释以下内容:

can someone, please explain the following:

我正在听丹·阿布拉莫夫 (Dan Abramov) 的讲座 &做练习.

I'm following Dan Abramov's lectures & doing the exercises.

代码工作正常，但是，当以下特定函数用大括号**{ }**编写时，测试失败.

The code works fine, however, the tests fail when the following particular function is written with curly brackets **{ }**.

    case 'toggleTodo' :
        return (
            state.map( (one) => {
                oneTodo( one, action )
            })
        );

相同的代码没有大括号就可以正常工作.

The same code works fine without curly brackets.

    case 'toggleTodo' :
        return (
            state.map( (one) => 
                oneTodo( one, action )
            )
        );

这里是 JsBin.请参阅第 31 行以后.

Here is the JsBin. Please refer to line 31 onwards.

推荐答案

case 'toggleTodo' :
    return (
        state.map( (one) => 
            oneTodo( one, action )
        )
    );

等于:

case 'toggleTodo' :
    return (
        state.map( (one) => {
            return oneTodo( one, action )
        })
    );

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