[英]Javascript object literal: what exactly is {a, b, c}?
The question I have is best given by way of this jsfiddle , the code for which is below:我的问题最好通过这个 jsfiddle 给出,其代码如下:
var a = 1, b = 'x', c = true;
var d = {a: a, b: b, c: c}; // <--- object literal
var e = [a, b, c]; // <--- array
var f = {a, b, c}; // <--- what exactly is this??
// these all give the same output:
alert(d.a + ', ' + d.b + ', ' + d.c );
alert(e[0] + ', ' + e[1] + ', ' + e[2]);
alert(f.a + ', ' + f.b + ', ' + f.c );
What sort of a data structure is f
? f
是什么类型的数据结构? Is it just a shorthand for d
?它只是
d
的简写吗?
var f = {a, b, c};
It came with ES6 (ECMAScript 2015) and means exactly the same as:它随 ES6 (ECMAScript 2015) 一起提供,含义与以下内容完全相同:
var f = {a: a, b: b, c: c};
It is called Object Literal Property Value Shorthands (or simply property value shorthand, shorthand properties).它被称为 Object Literal Property Value Shorthands(或简称为属性值速记,速记属性)。
You can also combine shorthands with classical initialization:您还可以将速记与经典初始化结合起来:
var f = {a: 1, b, c};
For more information see Object initializer .有关详细信息,请参阅对象初始化程序。
It is an Object Initializer Property Shorthand in ES6.它是 ES6 中的对象初始化器属性简写。
var f = {a, b, c, d:1}; // Will be equal to {a:a, b:b, c:c, d:1}
This works because the property value has the same name as the property identifier.这是有效的,因为属性值与属性标识符具有相同的名称。 This a new addition to the syntax of Object Initialiser (section 11.1.5 ) in the latest ECMAScript 6 draft Rev 13 .
这是最新的ECMAScript 6 草案 Rev 13中对Object Initialiser (第 11.1.5 节)语法的新增内容。 And of course, just like the limitations set from ECMAScript 3, you can't use a reserved word as your property name.
当然,就像 ECMAScript 3 中设置的限制一样,您不能使用保留字作为属性名称。
Such a shorthand won't dramatically change your code, it only makes everything a little bit sweeter!这样的速记不会显着改变你的代码,它只会让一切变得更甜蜜!
function createCar(name, brand, speed) {
return { type: 'Car', name: name, brand: brand, speed: speed };
}
// With the new shorthand form
function createSweetCar(name, brand, speed) {
return { type: 'Car', name, brand, speed }; // Yes it looks sweet.
}
Please see the compatibility table for support for these notations.请参阅兼容性表以获取对这些符号的支持。 In non-supporting environments, these notations will lead to syntax errors.
在不支持的环境中,这些符号会导致语法错误。
This shorthand notation offers object matching pretty nicely:这个速记符号很好地提供了对象匹配:
In ECMAScript5 what we used to do:在ECMAScript5中我们曾经做过的事情:
var tmp = getData();
var op = tmp.op;
var lhs = tmp.lhs;
var rhs = tmp.rhs;
Can be done in ECMAScript6 with a single line of code:可以在ECMAScript6中用一行代码完成:
var { op, lhs, rhs } = getData();
var f = {a, b, c}; // <--- what exactly is this??
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