Question

为什么当我在过滤器参数中添加花括号时，它不起作用？

// Write your code here:

function justCoolStuff(arr1,arr2){

  var newArray = arr1.filter(word => {arr2.includes(word)});
  return newArray

}






const coolStuff = ['gameboys', 'skateboards', 'backwards hats', 'fruit-by-the-foot', 'pogs', 'my room', 'temporary tattoos'];

const myStuff = [ 'rules', 'fruit-by-the-foot', 'wedgies', 'sweaters', 'skateboards', 'family-night', 'my room', 'braces', 'the information superhighway']; 

console.log(justCoolStuff(myStuff, coolStuff))

然而，当我删除大括号时，代码将运行。我以为是函数？这应该是正确的语法还是我弄错了？

// Write your code here:

function justCoolStuff(arr1,arr2){

  var newArray = arr1.filter((word) => arr2.includes(word));
  return newArray

}






const coolStuff = ['gameboys', 'skateboards', 'backwards hats', 'fruit-by-the-foot', 'pogs', 'my room', 'temporary tattoos'];

const myStuff = [ 'rules', 'fruit-by-the-foot', 'wedgies', 'sweaters', 'skateboards', 'family-night', 'my room', 'braces', 'the information superhighway']; 

console.log(justCoolStuff(myStuff, coolStuff))

Answer 1

你需要return语句 { return arr2.includes(word)}

Answer 2

添加大括号时，隐式 return 不再起作用。您需要手动返回，即：

var newArray = arr1.filter(word => { return arr2.includes(word) });

请参阅basic syntax of arrow functions。

Answer 3

如果您采用不同的格式，它可能会帮助您理解 - var newArray = arr1.filter(word => {arr2.includes(word)});

var newArray = arr1.filter(word => {
  arr2.includes(word)
});

如果你这样看，你就错过了 return 语句。使用括号，return 语句是隐含的。

Answer 4

箭头后面的大括号表示要执行的函数代码块。因此，在第一个示例中，您没有返回任何内容，因为您应该使用 return 关键字明确说明。但是，在第二个示例中，使用该语法时，可以理解您正在返回该布尔值，这正是过滤器方法所期望的。

Answer 5

因为那些被视为函数的开始，然后您隐式需要返回。

但这里有一些关于如何在不返回的情况下使用大括号的见解。

// Write your code here:

function justCoolStuff(arr1,arr2) {
    var newArray = arr1.filter(word => {
        return arr2.includes(word);
    });
    return newArray;
}

const coolStuff = ['gameboys', 'skateboards', 'backwards hats', 'fruit-by-the-foot', 'pogs', 'my room', 'temporary tattoos'];

const myStuff = [ 'rules', 'fruit-by-the-foot', 'wedgies', 'sweaters', 'skateboards', 'family-night', 'my room', 'braces', 'the information superhighway']; 

console.log(justCoolStuff(myStuff, coolStuff))

注意：

function doSomehting() {
  return 1;
}

// is equal to
const doSomething = () => 1;

// also equal to
const doSomething = () => {
  return 1;
}

// but not equal to
const doSomething = () => {
  1
}

需要 .filter() 方面的帮助

5 个答案: