noUnnecessaryConditions

JavaScript (and super languages)

摘要

¥Summary

规则生效日期：v2.1.4

¥Rule available since: v2.1.4
诊断类别：lint/nursery/noUnnecessaryConditions

¥Diagnostic Category: lint/nursery/noUnnecessaryConditions
此规则没有修复方案。

¥This rule doesn’t have a fix.
此规则的默认严重级别为 warning。

¥The default severity of this rule is warning.
此规则属于以下域：

¥This rule belongs to the following domains:
- project
来源：

¥Sources:
- 灵感来自 @typescript-eslint/no-unnecessary-condition
  
  ¥Inspired from @typescript-eslint/no-unnecessary-condition

如何配置

¥How to configure

1
{
2
  "linter": {
3
    "rules": {
4
      "nursery": {
5
        "noUnnecessaryConditions": "error"
6
      }
7
    }
8
  }
9
}

描述

¥Description

禁止使用静态方法判断为冗余的、不必要的基于类型的条件。

¥Disallow unnecessary type-based conditions that can be statically determined as redundant.

此规则检测条件语句中的表达式是否可静态推断，以及它们产生的真值或假值在程序生命周期内是否保持不变。

¥This rule detects if expressions inside conditions are statically inferrable and yield falsy or truthy values that don’t change during the life cycle of the program.

示例

¥Examples

无效

¥Invalid

1
function head<T>(items: T[]) {
2
  if (items) {  // This check is unnecessary
3
    return items[0].toUpperCase();
4
  }
5
}

1
function foo(arg: 'bar' | 'baz') {
2
  if (arg) {  // This check is unnecessary
3
  }
4
}

1
function bar(arg: string) {
2
  return arg?.length;  // ?. is unnecessary
3
}

与源规则不同，此规则不会触发分配给多个值的绑定。在以下示例中，变量 greeting 被赋予多个值；因此，它无法推断为真值或假值。

¥Contrary to the source rule, this rule doesn’t trigger bindings that are assigned to multiple values. In the following example, the variable greeting is assigned to multiple values; hence it can’t be inferred to a truthy or falsy value.

1
let greeting = false;
2

3
function changeGreeting() {
4
    greeting = "Hello World!"
5
}
6

7
if (greeting) {} // rule not triggered here

有效

¥Valid

1
function head<T>(items: T[] | null) {
2
  if (items) {  // This check is necessary
3
    return items[0].toUpperCase();
4
  }
5
}

1
function foo(arg: 'bar' | 'baz' | null) {
2
  if (arg) {  // This check is necessary
3
  }
4
}

1
function bar(arg: string | undefined) {
2
  return arg?.length;  // ?. is necessary
3
}

noUnnecessaryConditions

摘要

如何配置

描述

示例

无效

有效

相关链接