Why is the below returning undefined? Shouldn't I just get back [{name:'bug']?
var a= [{name:'dark'},{name:'bug'}]
a.map(function (obj) {
if (obj.name !== 'dark'){
return obj
}
})
//returns [undefined,{name:'bug}]
2 Answers
.map means you are mapping something for every item in an array. If you do not return anything, it will return undefined
If you wish to get certain values based on condition, you should use .filter
var a = [{
name: 'dark'
}, {
name: 'bug'
}]
var b = a.filter(function(obj) {
return obj.name !== 'dark'
})
console.log(b)Usage
- Map: if you wish to get some property of an object from an array of objects.
- Filter: If you wish to get specific values based on a condition. This will return array.
- Find: If you wish to get only first matching value. This will return element and not array.
- forEach: If you wish to loop over array and do specific processing.
Note: Most of array functions have compatibility issues and you should check it before using it.
References
7 Comments
mangocaptain
so there's no way to remove something from an arr with map? I should just use forEach and pop?
Rajesh Dixit
No. And it is not intended for this. If you wish to remove values, use
Array.filter@mangocaptain In general, you should not think in terms of "removing something from an array". You will end up splicing and slicing and popping and just confusing yourself. It's almost always better to think of creating a new array with just the elements you want, which is exactly what
filter does.
kevin ternet
Nevertheless, you could just insert a splice line in a forEach statement to remove a chosen object
|
you can use filter like this :
var a= [{name:'dark'},{name:'bug'}];
var b = a.filter(item => item.name != 'dark');
console.log(b); // [ { name: 'bug' } ]
mapwithfilter.