@typescript-eslint/no-unnecessary-condition

不允许使用类型始终为真或始终为假的表达式作为判断条件。

规则配置

// code-linter.json5
{
  "rules": {
    "@typescript-eslint/no-unnecessary-condition": "error"
  }
}

选项

详情请参考@typescript-eslint/no-unnecessary-condition选项。

正例

const index = 0;
export function head(items: readonly string[]): string {
  // Necessary, since items.length might be 0
  if (items.length) {
    return items[index].toUpperCase();
  } else {
    return '';
  }
}

export function foo(arg: string): void {
  // Necessary, since foo might be ''.
  if (arg) {
  }
}

export function bar(arg?: string | null) {
  // Necessary, since arg might be nullish
  return arg?.length;
}

反例

const index = 0;
export function head(items: readonly string[]) {
  // items can never be nullable, so this is unnecessary
  if (items) {
    return items[index].toUpperCase();
  } else {
    return '';
  }
}

export function foo(arg: 'bar' | 'baz') {
  // arg is never nullable or empty string, so this is unnecessary
  if (arg) {
  }
}

export function bar(arg: string) {
  // arg can never be nullish, so ?. is unnecessary
  return arg?.length;
}

规则集

plugin:@typescript-eslint/all

Code Linter代码检查规则的配置指导请参考Code Linter代码检查。