Undefined param of filter in AngularJS

Question

I have a filter in AngularJS but when I try to represent value in the view with this filter, I get undefined x.

My code:

.filter('param', function() {
    return function(x) {
        console.log(x);
        return x.split('__')[0];
    };
})

view

{{value | param}}

Result

angular.js:13920 TypeError: Cannot read property 'split' of undefined

I suspect it is that when loading the page I still do not have the value because it is obtained from a promise.

It probably isn't initialized yet when the filter first kicks of, as you say that value is resolved by a promise. This means that value first is undefined, and you cannot run .split on undefined. Just do a check in your filter: if(!x) return x — devqon
– devqon, Commented Jan 13, 2017 at 14:46

Karthik VU · Accepted Answer · 2017-01-13 15:01:20Z

2

This should help:

.filter('param', function() {
    return function(x) {
        if(x && typeof x === "string") return x.split('__')[0];
        else return x;
    };
})

Explanation :

You can apply the split function only of x has some value, in other terms, when x is not null or undefined.

Hence, we add a check to validate the variable x

edited Jan 13, 2017 at 15:01

answered Jan 13, 2017 at 14:54

Karthik VU

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3 Comments

ssc-hrep3 Over a year ago

if(x) only checks, if the value is truthy. if x is e.g. 1, it will crash.

maikelm Over a year ago

Right. But I'm sure value is a string. Anyway I used ngClock to wait for values to have value.

Karthik VU Over a year ago

You can never be sure :) Words of experience !

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