Typescript not operator not working

问题

I have this function that runs after a multiselect element is changed that sets an error message visibility:

  getVisibility(multiselect) {
    if ((multiselect.selectedCategories.length < 1 && !multiselect.allSelected) && this.submitted) {
      return 'visible'
    } else {
      return 'hidden'
    }
  }

However in this line:

if ((multiselect.selectedCategories.length < 1 && !multiselect.allSelected) && this.submitted)

multiselect.allSelected is false, but !multiselect.allSelected is also false.

picture1:

picture2:

Why is the ! (not) the same boolean value as without the not?

回答1:

Typescript not operator not working

Its just JavaScript in the end and it most definitely works. The issue with the chrome dev tools and / or TypeScript source maps.

What I do:

• Execute the command in the console (hovers can lie).
• Disable source maps (More reasons : Chrome Typescript debugging references wrong 'this')

来源：https://stackoverflow.com/questions/39186189/typescript-not-operator-not-working