如何使用ES6 Fat Arrow来.filter()一个对象数组 [英] How to use ES6 Fat Arrow to .filter() an array of objects
问题描述
我试图用 .filter
使用ES6箭头功能来返回成年人(Jack& Jill)。看来我不能使用if语句。
I'm trying to use ES6 arrow function with .filter
to return adults (Jack & Jill). It appears I cannot use an if statement.
为了在ES6中做到这一点,我需要知道什么?
What do I need to know in order to do this in ES6?
var family = [{"name":"Jack", "age": 26},
{"name":"Jill", "age": 22},
{"name":"James", "age": 5 },
{"name":"Jenny", "age": 2 }];
let adults = family.filter(person => if (person.age > 18) person); // throws error
(8:37) SyntaxError: unknown: Unexpected token (8:37)
|let adults = family.filter(person => if (person.age > 18) person);
我工作的ES5示例:
let adults2 = family.filter(function (person) {
if (person.age > 18) { return person; }
});
推荐答案
看起来我不能使用if语句。
It appears I cannot use an if statement.
箭头函数允许使用表达式 或 块作为其主体。传递表达式
Arrow functions either allow to use an expression or a block as their body. Passing an expression
foo => bar
相当于以下块
foo => { return bar; }
但是,
if (person.age > 18) person
不是表达式, 如果
是一个语句。因此,如果您想在箭头函数中使用 ,则必须使用块:
is not an expression, if
is a statement. Hence you would have to use a block, if you wanted to use if
in an arrow function:
foo => { if (person.age > 18) return person; }
虽然技术上解决了这个问题,混淆使用 .filter
,因为它建议您必须返回应包含在输出数组中的值。但是,传递给 .filter
的回调应该返回一个布尔值,即 true
或 false
,表示元素是否应该包含在新数组中。
While that technically solves the problem, this a confusing use of .filter
, because it suggests that you have to return the value that should be contained in the output array. However, the callback passed to .filter
should return a Boolean, i.e. true
or false
, indicating whether the element should be included in the new array or not.
所以你需要的只是
So all you need is
family.filter(person => person.age > 18);
在ES5中:
family.filter(function (person) {
return person.age > 18;
});
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