javascript：原始字符串有方法吗？ [英] javascript: do primitive strings have methods?

问题描述

MDN 声明：

原始值，原始值

不是对象且
没有任何方法的数据。 JavaScript有5
原始数据类型：string，number，
boolean，null，undefined。对于null和undefined的
异常，所有
基元值都具有对象
等价物，它包围
原始值，例如：一个String对象
包装一个字符串原语。所有
原语都是不可变的。

A data that is not an object and does not have any methods. JavaScript has 5 primitive datatypes: string, number, boolean, null, undefined. With the exception of null and undefined, all primitives values have object equivalents which wrap around the primitive values, e.g. a String object wraps around a string primitive. All primitives are immutable.

所以当我们调用s.replace 或s.anything 相当于 new String（s）。replace 和新字符串（s）。任何？

So when we call a "s".replace or "s".anything is it equivalent to new String("s").replace and new String("s").anything?

推荐答案

否，字符串原语没有方法。与数字原语一样，JavaScript运行时会通过以下结构将它们提升为完整的String对象：

No, string primitives do not have methods. As with numeric primitives, the JavaScript runtime will promote them to full-blown "String" objects when called upon to do so by constructs like:

var space = "hello there".indexOf(" ");

在某些语言中（特别是Java，但我认为这个术语是常用的）它是说该语言在适当的时候封装对象包装器中的原语。由于令牌语法的变幻莫测，数字有点复杂;你不能只说

In some languages (well, Java in particular, but I think the term is in common use) it's said that the language "boxes" the primitives in their object wrappers when appropriate. With numbers it's a little more complicated due to the vagaries of the token grammar; you can't just say

var foo = 27.toLocaleString();

因为。不会被解释为你需要它的方式;但是：

because the "." won't be interpreted the way you'd need it to be; however:

var foo = (27).toLocaleString();

工作正常。使用字符串原语—和布尔，就此而言 - —语法不含糊，例如：

works fine. With string primitives — and booleans, for that matter — the grammar isn't ambiguous, so for example:

var foo = true.toString();

将有效。

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