人们为什么在某些情况下会使用变量? [英] Why do people use variables in some cases?
问题描述
我知道这个问题的标题看起来很吓人，但事实并非如此.抱歉！
I know this question title looks scary, but it isn't. Sorry!
好吧，创建一次性的/不变的变量"有什么意义?
Ok, so, what's the point of creating a one-time-only/unchangeable "variable"?
让我们说我在Person对象中有一个名为"name"的属性.
Lets say I have one property called "name" in a Person object.
const Person = {
name: 'Luis Felipe Zaguini'
};
好的.因此，经常看到人们这样做:
Alright. So, it's incredibly common to see people doing this:
let personName = Person.name;
console.log(`I've written my name, and it is ${personName}.`);
就是这样.在大多数情况下，该变量仅使用一次.或者，有时，它在其他语句中被引用，但是您知道，它没有用，因为有一种无需设置新变量即可引用它的方法.
And that's it. In the majority of times that variable is used only once. Or, sometimes, it's referenced in other statements, but you know, it's useless because there IS a way to reference it without setting a new variable.
通常，您正在浪费CPU内存，将内存分配给无用的东西，因为实际上您可以多次键入Person.name并执行以下操作:
Tecnically, you're wasting CPU memory, allocating memory for something useless because you can, in fact, type Person.name multiple times, and do this:
console.log(`I've written my name, and it is ${Person.name}.`);
此外，您还浪费时间，在代码中添加了更多行.我太劳累了吗?很多程序员都在做这种事情，但是就我个人而言，这似乎不太适合.
Also, you're wasting time and adding more lines to your code. Am I overracting? Lot of programmers do this kind of stuff, but personally it doesn't seem to fit very well to me.
推荐答案
有多种原因
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'const`变量将防止该值意外更改，例如如果您编写了 closure ，其中包含在直接作用域之外可以访问的变量.
A 'const` variable will prevent the value from accidentally changing, e.g. if you have written a closure that includes a variable that is accessible outside immediate scope.
JavaScript引擎尚不能常见的子表达式消除，这是一种非常常见的编译器优化.使用临时变量可以提高性能，例如在此示例中.
Javascript engines are not yet capable of common subexpression elimination, which is a very common compiler optimization. Using a temporary variable could improve performance, like in this example.
有时，使用不同名称的变量可以阐明功能；请参见编写真正明显的代码(ROC).示例:
Sometimes a variable with a different name can clarify the functionality; see Writing Really Obvious Code (ROC). Example:
var activeUsername = User.name; //It's not just a user's name, it's the active user's name!
有时，额外的变量使调试/监视变量更加容易
Sometimes that extra variable makes it easier to debug/watch variables
有时候您想在分配过程中设置一个单独的断点
Sometimes you want to set a separate breakpoint during the assignment
我锻炼过度吗?
Am I overracting?
是的
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