函数的 JavaScript 参数内的花括号
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Curly braces inside JavaScript parameters for functions
提问by milan
What do the curly braces surrounding JavaScript parameters for functions do?
函数的 JavaScript 参数周围的花括号有什么作用？
var port = chrome.extension.connect({name: "testing"});
port.postMessage({found: (count != undefined)});
采纳答案by user113716
The curly braces denote an object literal. It is a way of sending key/value pairs of data.
花括号表示对象字面量。它是一种发送键/值对数据的方式。
So this:
所以这：
var obj = {name: "testing"};
Is used like this to access the data.
像这样用来访问数据。
obj.name; // gives you "testing"
You can give the object several comma separated key/value pairs, as long as the keys are unique.
您可以为对象提供多个逗号分隔的键/值对，只要键是唯一的。
var obj = {name: "testing",
another: "some other value",
"a-key": "needed quotes because of the hyphen"
};
You can also use square brackets to access the properties of the object.
您还可以使用方括号访问对象的属性。
This would be required in the case of the "a-key".
在"a-key".
obj["a-key"] // gives you "needed quotes because of the hyphen"
Using the square brackets, you can access a value using a property name stored in a variable.
使用方括号，您可以使用存储在变量中的属性名称访问值。
var some_variable = "name";
obj[ some_variable ] // gives you "testing"
回答by Matthias Winkelmann
A second possible answerhas arisen since this question was asked. Javascript ES6introduced Destructuring Assignment.
一个第二个可能的答案已经出现，因为这问题有人问。Javascript ES6引入了解构赋值。
var x = function({ foo }) {
console.log(foo)
}
var y = {
bar: "hello",
foo: "Good bye"
}
x(y)
Result: "Good bye"
回答by camomilk
Curly braces in javascript are used as shorthand to create objects. For example:
javascript 中的花括号用作创建对象的速记。例如：
// Create an object with a key "name" initialized to the value "testing"
var test = { name : "testing" };
alert(test.name); // alerts "testing"
Check out Douglas Crockford's JavaScript Surveyfor more detail.
查看 Douglas Crockford 的JavaScript 调查了解更多详情。
回答by hvgotcodes
var x = {title: 'the title'};
defines an object literal that has properties on it. you can do
定义一个具有属性的对象字面量。你可以做
x.title
which will evaluate to 'the title;
这将评估为'标题;
this is a common technique for passing configurations to methods, which is what is going on here.
这是将配置传递给方法的常用技术，这就是这里发生的事情。
