Operator '>' cannot be applied to types 'boolean' and 'number'?

Question

Im using this block in my html template :

  <div *ngIf="visibleblock && !selected?.item?.externalInfo?.length > 0">

But im getting this error when i do:

ng build --prod --aot

Any suggestion how can i fix this ?

Why the `!` before `selected?.item?.externalInfo?.length` – Starfish Aug 31 '17 at 06:37 — Starfish, Aug 31 '17 at 06:37

score 41 · Accepted Answer · answered Aug 31 '17 at 06:38

41

Put the second expression inside parenthesis:

<div *ngIf="visibleblock && !(selected?.item?.externalInfo?.length > 0)">

answered Aug 31 '17 at 06:38

FAISAL

Its working.. Can you explain what is the difference between these ? – Krunal Dec 21 '18 at 07:18
4

@Krunal For example: `!a.length` returns a boolean value because it will check if the length of `a` exists. So writing `(!a.length > 0)` will compare a boolean value to 0. `!(a.length > 0)` will check if the comparison inside the paranthesis (number versus number) is a boolean value true or false. That's the difference and that's why OP got an error message. – mahval Jan 16 '19 at 13:10

1 Answers1