angular2教程，const变量的样式指南

Question

Accord Style guide angular2, tells: "Consider spelling const variables in lower camel case." "The tradition of naming constants in UPPER_SNAKE_CASE reflects an era before the modern IDEs that quickly reveal the const declaration. TypeScript itself prevents accidental reassignment"

https://angular.io/styleguide#!#03-02

but in angular2 tutorial use for app.component.ts file (hero array), use UPPER_SNAKE_CASE

    import { Hero } from './hero';
    export const HEROES: Hero[] = [
        {id: 11, name: 'Mr. Nice'},
        {id: 12, name: 'Narco'},
        {id: 13, name: 'Bombasto'},
        {id: 14, name: 'Celeritas'},
        {id: 15, name: 'Magneta'},
        {id: 16, name: 'RubberMan'},
        {id: 17, name: 'Dynama'},
        {id: 18, name: 'Dr IQ'},
        {id: 19, name: 'Magma'},
        {id: 20, name: 'Tornado'}
    ];

why?

Answer 1

Imho there's a difference between naming a const containing a literal / a structure of literals or a const coming from variables:

I'd UPPER_SNAKE_CASE this:

const API_URL = "http://www.example.com";

And lowerCamelCase this:

for (var i = 0; i < 10; i++) {
  const maxHeightOfVehicle = bridges[i].height - 10;

  console.log(maxHeightOfVehicle);
}

Although maxHeightOfVehicle is technically a constant, it doesn't mean that it won't have different values over time.

API_URL on the other hand is a literal making it a "real constant";

So although it's not needed anymore to prevent you from changing a constant, it still tells you something about what you're dealing with.

So in the tour of heroes case I'd prefer keeping HEROES in UPPERCASE because it's a structure of literals. a well-defined constant.