AngularJS ng-if problems with 'f' and 'F'

Question

Can anybody explain to me why Angularjs ngIf directive reads 'f' and 'F' like false?

Simple example which does not work:

  <input type="text" ng-model="test" />
  <div ng-if="test">{{test}}<div>

If you put 'f' or 'F' nothing shows in div, any other letter or sine works ok.

Demo: http://plnkr.co/edit/wS4PqmARXG2fsblUkLpH?p=preview

Answer 1

ngIf uses toBoolean check internally. Here is toBoolean itself:

function toBoolean(value) {
  if (typeof value === 'function') {
    value = true;
  } else if (value && value.length !== 0) {
    var v = lowercase("" + value);
    value = !(v == 'f' || v == '0' || v == 'false' || v == 'no' || v == 'n' || v == '[]');
  } else {
    value = false;
  }
  return value;
}

As you can see, there will be an issue not only with f letter, but also with '0', 'no', 'n', etc. It's not going to be fixed though. However toBoolean is likely to be removed in future versions.

See this discussion on Github: https://github.com/angular/angular.js/issues/1229?source=cc

Answer 2

I found simple solution to resolve my problem with validation by that:

<input type="text" ng-model="test" />
<div ng-if="test.length > 0">TEST: {{test}}<div>

plunker: http://plnkr.co/edit/epDLYitkhCDMJJebfSON?p=preview