prefer-as-const
NOTE: this rule is part of the
推荐 rule set.Enable full set in
deno.json:{
"lint": {
"rules": {
"tags": ["推荐"]
}
}
}Enable full set using the Deno CLI:
deno lint --rules-tags=推荐
This rule can be explictly included to or excluded from the rules present in the current tag by adding it to the
include or exclude array in deno.json:{
"lint": {
"rules": {
"include": ["prefer-as-const"],
"exclude": ["prefer-as-const"]
}
}
}推荐使用常量断言（as const）而不是显式指定字面量类型或使用类型断言。
在声明一个新的原始字面量类型变量时，有三种方式：
- 添加显式类型注解
- 使用普通类型断言（如
as "foo"或<"foo">） - 使用常量断言（
as const）
此 lint 规则建议使用常量断言，因为这通常会导致更安全的代码。有关常量断言的更多细节，请参见 官方手册。
无效：
let a: 2 = 2; // 类型注解
let b = 2 as 2; // 类型断言
let c = <2> 2; // 类型断言
let d = { foo: 1 as 1 }; // 类型断言
有效：
let a = 2 as const;
let b = 2 as const;
let c = 2 as const;
let d = { foo: 1 as const };
let x = 2;
let y: string = "hello";
let z: number = someVariable;