这个节点文档中的... ... $ {...} ...`代码是什么意思? [英] What does this `…${…}…` code in the node docs mean?
问题描述
reqiure(moduleName)
函数。 我看了看文档,并在示例文档中找到一些奇怪的代码:
const circle = require('./ circle.js');
console.log(`半径为4的圆的面积是$ {circle.area(4)}`);
更具体地说, $ {circle.area(4)}
bit。
从我所理解的JavaScript中的 $
就像任何其他变量一样。当我们在客户端Web开发中使用它时,它被用作文档功能的代理(我认为)。使用节点分配给什么?
除此之外,这个语法是什么意思? $ {circle.area(4)}
如果 $
只是引用一些函数 someFunction()
,不会等于这个 someFunction(){cirle.area(4) }
。我没有看到这可以是有效的语法。
另外,为什么不直接调用 circle.area()
函数直接反正?
这是:
`半径为4的圆圈的面积是$ {circle.area(4)}`
内插任何 circle.area(4)
直接表示到字符串中。如果您对这个或其他ES2015功能感到好奇,建议您查看 Babel 并在REPL中播放。
你可以看到这个ES2015代码:
const foo ='some text';
console.log(`$ {foo}被插入。
被折叠到其ES5等价物 - 一个简单的 +
concatenation:
var foo ='some text';
console.log(foo +'被插值。
I am to trying to learn Express library and Node.js one step at a time. First I am looking at is the specifics of the Node reqiure(moduleName)
function.
I took a look at the documentation for this, and found some weird code in the example documentation:
const circle = require('./circle.js');
console.log( `The area of a circle of radius 4 is ${circle.area(4)}`);
More specifically the ${circle.area(4)}
bit.
From what I understand the $
in JavaScript is just like any other variable. When we are using it on client side web development it is used as a delegate for the document function (I think). What is it assigned to when using node?
On top of that, what does this syntax mean? ${circle.area(4)}
If $
is just a reference to some function someFunction()
, wouldn't it be equivalent to this someFunction(){cirle.area(4)}
. I am not seeing how that could be valid syntax.
Also, why wouldn't they just directly call the circle.area()
function directly anyways?
This:
`The area of a circle of radius 4 is ${circle.area(4)}`
is an example of ES2015 template strings.
It interpolates whatever circle.area(4)
represents directly into the string. If you're curious about this or other ES2015 features, I recommend checking out Babel and playing around in the REPL.
Here's a very simple example to get you started.
You can see this ES2015 code:
const foo = 'some text';
console.log(`${foo} is interpolated.`);
is transpiled to its ES5 equivalent - a simple +
concatenation:
var foo = 'some text';
console.log(foo + ' is interpolated.');
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