Finding and Removing Object From Array with Specified Date Key

Question

I have a JavaScript array of objects that has ISO 8601 date strings as keys, and a number for the value like this:

var myArray = [
  {"Wed May 27 2015 04:46:04 GMT+0000 (UTC)":1.1},
  {"Wed May 24 2015 10:34:04 GMT+0000 (UTC)":2.2}
]

I want to find and remove any objects that match a certain date like this:

var myDate = "Wed May 27 2015 04:46:04 GMT+0000 (UTC)"

if(myDate is a key in myArray){
  //Remove it from myArray
}

And the result would be that myArray now looks like this:

[{"Wed May 24 2015 10:34:04 GMT+0000 (UTC)":2.2}]

I have Underscore JS available, but I can't figure this out.

Hmm... are they the wrong format? I'm using Parse, and this is the format it returns and they claim their Date data type is ISO 8601. — Clifton Labrum
– Clifton Labrum, Commented May 27, 2015 at 7:10
ISO 8601 Universal datetime template: YYYY-MM-ddThh:mm:ssZ. new Date().toJSON() returns current date/time in ISO 8601. But new Date().toString() returns current date/time in human format like in your code snippets. — dizel3d
– dizel3d, Commented May 27, 2015 at 7:18

thefourtheye · Accepted Answer · 2015-05-27 06:02:36Z

3

You can use _.filter, _.has, _.partial and _.negate methods, like this

console.log(_.filter(myArray, _.partial(_.negate(_.has), _, myDate)));
// [ { 'Wed May 24 2015 10:34:04 GMT+0000 (UTC)': 2.2 } ]

Here, _.negate(_.has) will return a new function which will just negate the result of _.has always.
_.partial(_.negate(_.has), _, myDate) will return a new function which will accept the values from myArray in the placeholder _ and _.has will be invoked with the value from the myArray and myDate as arguments.
_.has will return true if the object passed as the first argument has a key with the same name as the second parameter passed to it.

For older version of _

If you are using an older version of _, then you can simply pass a function object to do this,

console.log(_.filter(myArray, function(currentObject) {
    return !_.has(currentObject, myDate);
}));
// [ { 'Wed May 24 2015 10:34:04 GMT+0000 (UTC)': 2.2 } ]

Vanila JS Version

console.log(myArray.filter(function(currenObject) {
    return !currenObject.hasOwnProperty(myDate);
}));
// [ { 'Wed May 24 2015 10:34:04 GMT+0000 (UTC)': 2.2 } ]

You can simply use Array.prototype.filter function and check if the current object has a property with the value of myDate, with Object.prototype.hasOwnProperty.

If you are sure that the myDate will not have a value which will not be one of the inherited properties of Object, then you can also use in operator, like this

console.log(myArray.filter(function(currenObject) {
    return !(myDate in currenObject);
}));
// [ { 'Wed May 24 2015 10:34:04 GMT+0000 (UTC)': 2.2 } ]

edited May 27, 2015 at 6:02

answered May 27, 2015 at 5:12

thefourtheye

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4 Comments

Clifton Labrum Over a year ago

Thanks for your help. :) I had to use the filter version since I have an older version of Underscore. The only catch is that your solution is returning the value matching myDate instead of removing that value from the array.

thefourtheye Over a year ago

You can assign the result to myArray. The advantage here is we don't mutate the original object

Clifton Labrum Over a year ago

I've done that, but again, it's having the opposite effect. It's returning an array with myDate in it instead of an array without myDate in it.

thefourtheye Over a year ago

@CliftonLabrum Okay, I updated the original _ version with _.negate and other versions with the native logical not operator (!). Please check now.

Newinjava · Accepted Answer · 2015-05-27 05:26:27Z

1

I don't know about the underscoreJs, but I hope this simple way will help you out.

var myArray = [
              {"Wed May 27 2015 04:46:04 GMT+0000 (UTC)":1.1},
              {"Wed May 24 2015 10:34:04 GMT+0000 (UTC)":2.2}
            ];
var myDate = "Wed May 27 2015 04:46:04 GMT+0000 (UTC)";

for(i=0;i<myArray.length;i++)
{
    if(myDate == Object.keys(myArray[i]))
    {
        myArray.splice(i,1);
    }
}

answered May 27, 2015 at 5:26

Newinjava

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