[英]return object from array map
Suppose I could hardcode the following:假设我可以硬编码以下内容:
const data = [ { a: 0, b: 1}, {a:2,b:3},... ]
But I have the data in an array, and I would like to write something like the following:但是我有一个数组中的数据,我想写如下内容:
const data = my_arr.map((element,index) => { a:element, b:index});
How does one yield this kind of object from an array map?如何从数组映射中产生这种对象?
You just need to add parenthesis around the returned object literal.您只需要在返回的对象文字周围添加括号。
const my_arr = [1,2,3,4,5]; const data = my_arr.map((element, index) => ({ a: element, b:index })); // ^ ^ console.log(data);
The reason is that the JavaScript parser rules assume that the {
following the =>
is the start of a function body.原因是 JavaScript 解析器规则假定
=>
后面的{
是函数体的开始。 To go around this, we wrap the object in ()
(alternatively we can add a return
statement)为了解决这个问题,我们将对象包装在
()
(或者我们可以添加一个return
语句)
Read more here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions#Returning_object_literals在此处阅读更多信息: https : //developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions#Returning_object_literals
Ah, figured this out.啊,想通了。
The anonymous object clashes with the scope operators, so you need to encapsulate the object in a scope block, and pass the object by return from there:匿名对象与作用域运算符发生冲突,因此您需要将对象封装在作用域块中,并通过从那里返回来传递对象:
const data = my_arr.map((element,index) => { return {a:element,b:index}});
You have to add parenthesis around your returned object to differentiate it from a simple block:您必须在返回的对象周围添加括号以将其与简单块区分开来:
const my_arr = [1, 2, 4, 3, 4]; const data = my_arr.map((element, index) => ({ a: element, b: index })); console.log(data);
Or return it explicitly :或者明确返回:
const my_arr = [1, 2, 4, 3, 4]; const data = my_arr.map((element, index) => { return { a: element, b: index }; }); console.log(data);
I guess it's the same我想是一样的
var my_arr = [...Array(5).keys()] var result = my_arr.map((element,index) => ({ a: element, b: element + 1 })); console.log('result', result)
So, it works所以,它有效
See output:见输出:
var results = []; [...Array(11).keys()].forEach((el) => { if (el % 2 === 0) { results.push({ a: el, b: el + 1 }) } }) console.log('results',results)
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