Why Math.floor return nothing when we write it into HTML angular?

Question

Here is my HTML:

<div ng-controller = "myCntrl">  
    <pre>floor 1: {{Math.floor( value )  }}</pre>  
    <pre>floor 2: {{value }}</pre>  
    <pre>floor 3: {{value | number : 0 }}</pre>  
    <pre>floor 1 from controller: {{newValue }}</pre>  
</div>

Controller

app.controller('myCntrl', function ($scope) {
    $scope.value = 1233.8435;
    $scope.newValue = Math.floor(1233.8435);    
});

The output:

floor 1: 
floor 2: 1233.8435
floor 3: 1,234
floor 1 from controller: 1233

Generally I'm looking for the proper way to get 1233.

I don't want to invoke new method in controller.

Why Math.floor returns nothing?

Thanks,

Demo Fiddle

Also, http://stackoverflow.com/questions/12740329/math-functions-in-angular-bindings — Sergiu Paraschiv, Nov 25 '13 at 15:49
This should actually be included in the Angular docs: *"expressions are not JavaScript `eval`. Check out the following example..."* — Kos Prov, Nov 25 '13 at 15:51
Actually, it is: "It might be tempting to think of Angular view expressions as JavaScript expressions, but that is not entirely correct, since Angular does not use a JavaScript eval() to evaluate expressions." (http://docs.angularjs.org/guide/expression) — Sergiu Paraschiv, Nov 25 '13 at 15:53
You are correct. I'm just saying that they should include this very example in it. :P — Kos Prov, Nov 25 '13 at 16:01

score 19 · Answer 1 · answered Nov 25 '13 at 15:46

19

In this case, AngularJS <span>{{value}}</span> (expression) is shorthand for <span ng-bind="value"></span> and ng-bind acts on the current scope.

Your current scope is the one defined by myCntrl so ng-bind="value" is evaluated as $scope.value.

AngularJS has no way of making a distinction between the global Math namespace and $scope.Math, so it treats it like any other scoped expression.

I'd advise against using $scope.Math=Math;.

The correct way to do it is using a filter:

angular.module('myApp',[]).filter('floor', function(){

    return function(n){
        return Math.floor(n);
    };
});

answered Nov 25 '13 at 15:46

Sergiu Paraschiv

9,929
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1

+1 for that. Maybe you could skip the wrapper function and return `Math.floor;` – Kos Prov Nov 25 '13 at 16:02
+1 for doing it the angular way. This is a much better answer than the accepted answer. – brcpar Jul 01 '14 at 03:42

score 13 · Accepted Answer · answered Nov 25 '13 at 15:38

13

Expressions are evaluated on the $scope. If you do this in your controller

$scope.Math=Math;

it would work.

answered Nov 25 '13 at 15:38

Chandermani

42,589
12
85
88

score 1 · Answer 3 · answered Nov 25 '13 at 15:41

Put it in your controller

<div ng-controller = "myCntrl">  
  <pre>floor 1: {{Mathvalue}}</pre>  
  <pre>floor 2: {{value }}</pre>  
  <pre>floor 3: {{value | number : 0 }}</pre>  
</div>

var app = angular.module('myModule', []);

app.controller('myCntrl', function ($scope) {
  $scope.value = 1233.8435; 
  $scope.Mathvalue = Math.floor(1233.8435);
});

app.$inject = ['$scope'];

score 0 · Answer 4 · answered Nov 25 '13 at 15:39

0

Angular expression doesn't support all javascript method, for example Math.floor(), you can declear a floor function on your $scope and delegete Meth floor

answered Nov 25 '13 at 15:39

Sean

2,990
1
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31

Why Math.floor return nothing when we write it into HTML angular?

4 Answers4

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